/*
输入文件见337.in.txt
输出文件见338.out.txt
*/
#include <iostream>
#include <cctype>
#include <fstream>
#include <cstring>
using namespace std;
* + ; //单词表的最大值
+ ; //单词长度的最大值
struct WordList
{
char word[maxWord]; //单词
int fre; //词频
} list[maxList];
char *Delete(char *str,char c) //删除一个单词中的标点符号. 如: declicious! 删去！
{
char *p = str; //声明一个指针指向自己
char *p2 = str; //如果str自己移动指针的话，最后返回str时，返回的是尾指针，输出为空
while (*p2)
{
if (*p2 == c)
p2++;
else
*p++ = *p2++;
}
*p = '\0';
return str;
}
//因为单词长度不同,所以此函数用来规范输出格式
)
{
out << w.word;
; i < findMax - len; i++)
{
out << extra;
}
out << w.fre << endl;
}
int main()
{
ifstream in("337.in.txt"); //读取单词文件
ofstream out("337.out.txt"); //写入单词及其个数文件
if (!in) {
cout << ;
}
// WordList list[maxList]; //单词表
; //单词的数量
, lenTmp = ; //查找最大字符串长度
;
string wordMax;
char tmp[maxWord]; //读取单词
while (in >> tmp)
{
int i;
lenTmp = strlen(tmp);
if (findMax < lenTmp) findMax = lenTmp;
// if( !isalpha( tmp[strlen(tmp)-1]) ) //最后一个字符位置不是单词
// Delete(tmp, tmp[strlen(tmp)-1]); //删去一个单词后的标点符号
; i < N; i++) //在单词表中查找该单词
{
) { //找到则，fre++；
list[i].fre++;
if (wordFreMax < list[i].fre) {
wordFreMax = list[i].fre;
wordMax = list[i].word;
}
break;
}
}
if (i == N) // && isalpha(tmp[0]) 找不到则添加该单词,且该词频置为1,单词表数目N++
{ //标点符号不统计
strcpy(list[N].word, tmp);
list[N++].fre = ;
}
}
out << "单词表总数:\t" << N << "\n单词频率最高:\t" << wordMax << "\t次数:\t" << wordFreMax << endl;
out << "所有单词为:";
; i < findMax - ; i++)
out << ' ';
out << "单词数为:\n";
; i < N; i++)
{
ShowOrder(list[i], ' ', strlen(list[i].word), out, findMax); //标准化输出
}
;
}
//337.in.txt ---- 测试输入数据
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Reference<deque>deque
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class template :
<deque> ?
std::deque !
template < class T, class Alloc = allocator<T> > class deque;
Double ended queue
deque (usually pronounced like "deck") is an irregular acronym of double-ended queue. Double-ended queues are sequence containers with dynamic sizes that can be expanded or contracted on both ends (either its front or its back).
Specific libraries may implement deques in different ways, generally as some form of dynamic array. But in any case, they allow for the individual elements to be accessed directly through random access iterators, with storage handled automatically by expanding and contracting the container as needed.
Therefore, they provide a functionality similar to vectors, but with efficient insertion and deletion of elements also at the beginning of the sequence, and not only at its end. But, unlike vectors, deques are not guaranteed to store all its elements in contiguous storage locations: accessing elements in a deque by offsetting a pointer to another element causes undefined behavior.
Both vectors and deques provide a very similar interface and can be used for similar purposes, but internally both work in quite different ways: While vectors use a single array that needs to be occasionally reallocated for growth, the elements of a deque can be scattered in different chunks of storage, with the container keeping the necessary information internally to provide direct access to any of its elements in constant time and with a uniform sequential interface (through iterators). Therefore, deques are a little more complex internally than vectors, but this allows them to grow more efficiently under certain circumstances, especially with very long sequences, where reallocations become more expensive.
For operations that involve frequent insertion or removals of elements at positions other than the beginning or the end, deques perform worse and have less consistent iterators and references than lists and forward lists.
Container properties
Sequence
Elements in sequence containers are ordered in a strict linear sequence. Individual elements are accessed by their position in this sequence.
Dynamic array
Generally implemented as a dynamic array, it allows direct access to any element in the sequence and provides relatively fast addition/removal of elements at the beginning or the end of the sequence.
Allocator-aware
The container uses an allocator object to dynamically handle its storage needs.
Template parameters
T
Type of the elements.
Aliased as member type deque::value_type.
Alloc
Type of the allocator object used to define the storage allocation model. By default, the allocator class template is used, which defines the simplest memory allocation model and is value-independent.
Aliased as member type deque::allocator_type.
Member types
C++98C++
member type definition notes
value_type The first template parameter (T)
allocator_type The second template parameter (Alloc) defaults to: allocator<value_type>
reference allocator_type::reference for the default allocator: value_type&
const_reference allocator_type::const_reference for the default allocator: const value_type&
pointer allocator_type::pointer for the default allocator: value_type*
const_pointer allocator_type::const_pointer for the default allocator: const value_type*
iterator a random access iterator to value_type convertible to const_iterator
const_iterator a random access iterator to const value_type
reverse_iterator reverse_iterator<iterator>
const_reverse_iterator reverse_iterator<const_iterator>
difference_type a signed integral type, identical to: iterator_traits<iterator>::difference_type usually the same as ptrdiff_t
size_type an unsigned integral type that can represent any non-negative value of difference_type usually the same as size_t
Member functions
(constructor)
Construct deque container (public member function )
(destructor)
Deque destructor (public member function )
operator=
Assign content (public member function )
Iterators:
begin
Return iterator to beginning (public member function )
end
Return iterator to end (public member function )
rbegin
Return reverse iterator to reverse beginning (public member function )
rend
Return reverse iterator to reverse end (public member function )
cbegin
Return const_iterator to beginning (public member function )
cend
Return const_iterator to end (public member function )
crbegin
Return const_reverse_iterator to reverse beginning (public member function )
crend
Return const_reverse_iterator to reverse end (public member function )
Capacity:
size
Return size (public member function )
max_size
Return maximum size (public member function )
resize
Change size (public member function )
empty
Test whether container is empty (public member function )
shrink_to_fit
Shrink to fit (public member function )
Element access:
operator[]
Access element (public member function )
at
Access element (public member function )
front
Access first element (public member function )
back
Access last element (public member function )
Modifiers:
assign
Assign container content (public member function )
push_back
Add element at the end (public member function )
push_front
Insert element at beginning (public member function )
pop_back
Delete last element (public member function )
pop_front
Delete first element (public member function )
insert
Insert elements (public member function )
erase
Erase elements (public member function )
swap
Swap content (public member function )
clear
Clear content (public member function )
emplace
Construct and insert element (public member function )
emplace_front
Construct and insert element at beginning (public member function )
emplace_back
Construct and insert element at the end (public member function )
Allocator:
get_allocator
Get allocator (public member function )
Non-member functions overloads
relational operators
Relational operators for deque (function )
swap
Exchanges the contents of two deque containers (function template )
C++
Information
Tutorials
Reference
Articles
Forum
Reference
C library:
Containers:
<array>
<deque>
<forward_list>
<list>
<map>
<queue>
<set>
<stack>
<unordered_map>
<unordered_set>
<vector>
Input/Output:
Multi-threading:
Other:
<deque>
deque
deque
deque::deque
deque::~deque
member functions:
deque::assign
deque::at
deque::back
deque::begin
deque::cbegin
deque::cend
deque::clear
deque::crbegin
deque::crend
deque::emplace
deque::emplace_back
deque::emplace_front
deque::empty
deque::end
deque::erase
deque::front
deque::get_allocator
deque::insert
deque::max_size
deque::operator=
deque::operator[]
deque::pop_back
deque::pop_front
deque::push_back
deque::push_front
deque::rbegin
deque::rend
deque::resize
deque::shrink_to_fit
deque::size
deque::swap
non-member overloads:
relational operators (deque)
swap (deque)
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QObject Class
The QObject class is the base class of all Qt objects. More...
Header: #include <QObject>
qmake: QT += core
Instantiated By: QtObject
Inherited By:
Q3DObject, Q3DScene, Q3DTheme, QAbstract3DAxis, QAbstract3DInputHandler, QAbstract3DSeries, QAbstractAnimation, QAbstractAxis, QAbstractDataProxy, QAbstractEventDispatcher, QAbstractItemDelegate, QAbstractItemModel, QAbstractMessageHandler, QAbstractNetworkCache, QAbstractSeries, QAbstractState, QAbstractTextDocumentLayout, QAbstractTransition, QAbstractUriResolver, QAbstractVideoFilter, QAbstractVideoSurface, QAccessiblePlugin, QAction, QActionGroup, QAudioInput, QAudioOutput, QAudioProbe, QAxFactory, QAxObject, QAxScript, QAxScriptManager, QBarSet, QBluetoothDeviceDiscoveryAgent, QBluetoothLocalDevice, QBluetoothServer, QBluetoothServiceDiscoveryAgent, QBluetoothTransferManager, QBluetoothTransferReply, QBoxSet, QButtonGroup, QCameraExposure, QCameraFocus, QCameraImageCapture, QCameraImageProcessing, QCanBus, QCanBusDevice, QClipboard, QCompleter, QCoreApplication, QCustom3DItem, QDataWidgetMapper, QDBusAbstractAdaptor, QDBusAbstractInterface, QDBusPendingCallWatcher, QDBusServer, QDBusServiceWatcher, QDBusVirtualObject, QDesignerFormEditorInterface, QDesignerFormWindowManagerInterface, QDnsLookup, QDrag, QEventLoop, QExtensionFactory, QExtensionManager, QFileSelector, QFileSystemWatcher, QGamepad, QGenericPlugin, QGeoAreaMonitorSource, QGeoCodeReply, QGeoCodingManager, QGeoCodingManagerEngine, QGeoPositionInfoSource, QGeoRouteReply, QGeoRoutingManager, QGeoRoutingManagerEngine, QGeoSatelliteInfoSource, QGeoServiceProvider, QGesture, QGLShader, QGLShaderProgram, QGraphicsAnchor, QGraphicsEffect, QGraphicsItemAnimation, QGraphicsObject, QGraphicsScene, QGraphicsTransform, QHelpEngineCore, QHelpSearchEngine, QHttpMultiPart, QIconEnginePlugin, QImageIOPlugin, QInAppProduct, QInAppStore, QInAppTransaction, QInputMethod, QIODevice, QItemSelectionModel, QJSEngine, QLayout, QLegendMarker, QLibrary, QLocalServer, QLowEnergyController, QLowEnergyService, QMacToolBar, QMacToolBarItem, QMaskGenerator, QMediaControl, QMediaObject, QMediaPlaylist, QMediaRecorder, QMediaService, QMediaServiceProviderPlugin, QMimeData, QModbusDevice, QModbusReply, QMovie, QNearFieldManager, QNearFieldShareManager, QNearFieldShareTarget, QNearFieldTarget, QNetworkAccessManager, QNetworkConfigurationManager, QNetworkCookieJar, QNetworkSession, QObjectCleanupHandler, QOffscreenSurface, QOpenGLContext, QOpenGLContextGroup, QOpenGLDebugLogger, QOpenGLShader, QOpenGLShaderProgram, QOpenGLTimeMonitor, QOpenGLTimerQuery, QOpenGLVertexArrayObject, QPdfWriter, QPictureFormatPlugin, QPieSlice, QPlaceManager, QPlaceManagerEngine, QPlaceReply, QPlatformGraphicsBuffer, QPlatformSystemTrayIcon, QPluginLoader, QQmlComponent, QQmlContext, QQmlExpression, QQmlExtensionPlugin, QQmlFileSelector, QQmlNdefRecord, QQmlPropertyMap, QQuickImageResponse, QQuickItem, QQuickItemGrabResult, QQuickRenderControl, QQuickTextDocument, QQuickTextureFactory, QQuickWebEngineProfile, QRadioData, QScreen, QScriptEngine, QScriptEngineDebugger, QScriptExtensionPlugin, QScroller, QScxmlDataModel, QScxmlStateMachine, QSensor, QSensorBackend, QSensorGesture, QSensorGestureManager, QSensorGestureRecognizer, QSensorReading, QSessionManager, QSettings, QSGAbstractRenderer, QSGEngine, QSGTexture, QSGTextureProvider, QSharedMemory, QShortcut, QSignalMapper, QSignalSpy, QSocketNotifier, QSound, QSoundEffect, QSqlDriver, QSqlDriverPlugin, QStyle, QStyleHints, QStylePlugin, QSvgRenderer, QSyntaxHighlighter, QSystemTrayIcon, Qt3DCore::QAbstractAspect, Qt3DCore::QAspectEngine, Qt3DCore::QNode, Qt3DCore::Quick::QQmlAspectEngine, Qt3DInput::QKeyEvent, Qt3DInput::QMouseEvent, Qt3DInput::QWheelEvent, Qt3DRender::QGraphicsApiFilter, Qt3DRender::QPickEvent, Qt3DRender::QTextureWrapMode, QTcpServer, QTextDocument, QTextObject, QThread, QThreadPool, QTimeLine, QTimer, QTranslator, QtVirtualKeyboard::InputContext, QtVirtualKeyboard::InputEngine, QtVirtualKeyboard::ShiftHandler, QUiLoader, QUndoGroup, QUndoStack, QValidator, QValue3DAxisFormatter, QVideoProbe, QWaylandClient, QWaylandSurfaceGrabber, QWaylandView, QWebChannel, QWebChannelAbstractTransport, QWebEngineCookieStore, QWebEngineDownloadItem, QWebEnginePage, QWebEngineProfile, QWebEngineUrlRequestInterceptor, QWebEngineUrlRequestJob, QWebEngineUrlSchemeHandler, QWebSocket, QWebSocketServer, QWidget, QWindow, QWinEventNotifier, QWinJumpList, QWinTaskbarButton, QWinTaskbarProgress, QWinThumbnailToolBar, and QWinThumbnailToolButton
List of all members, including inherited members
Obsolete members
Note: All functions in this class are reentrant.
Note: These functions are also thread-safe:
connect(const QObject *sender, const char *signal, const QObject *receiver, const char *method, Qt::ConnectionType type)
connect(const QObject *sender, const char *signal, const char *method, Qt::ConnectionType type)
connect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method, Qt::ConnectionType type)
connect(const QObject *sender, PointerToMemberFunction signal, Functor functor)
connect(const QObject *sender, PointerToMemberFunction signal, const QObject *context, Functor functor, Qt::ConnectionType type)
disconnect(const QObject *sender, const char *signal, const QObject *receiver, const char *method)
disconnect(const char *signal, const QObject *receiver, const char *method)
disconnect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method)
Properties
objectName : QString
Public Functions
QObject(QObject *parent = Q_NULLPTR)
virtual ~QObject()
bool blockSignals(bool block)
const QObjectList & children() const
QMetaObject::Connection connect(const QObject *sender, const char *signal, const char *method, Qt::ConnectionType type = Qt::AutoConnection) const
bool disconnect(const char *signal = Q_NULLPTR, const QObject *receiver = Q_NULLPTR, const char *method = Q_NULLPTR) const
bool disconnect(const QObject *receiver, const char *method = Q_NULLPTR) const
void dumpObjectInfo()
void dumpObjectTree()
QList<QByteArray> dynamicPropertyNames() const
virtual bool event(QEvent *e)
virtual bool eventFilter(QObject *watched, QEvent *event)
T findChild(const QString &name = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
QList<T> findChildren(const QString &name = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
QList<T> findChildren(const QRegExp ®Exp, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
QList<T> findChildren(const QRegularExpression &re, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
bool inherits(const char *className) const
void installEventFilter(QObject *filterObj)
bool isWidgetType() const
bool isWindowType() const
void killTimer(int id)
virtual const QMetaObject * metaObject() const
void moveToThread(QThread *targetThread)
QString objectName() const
QObject * parent() const
QVariant property(const char *name) const
void removeEventFilter(QObject *obj)
void setObjectName(const QString &name)
void setParent(QObject *parent)
bool setProperty(const char *name, const QVariant &value)
bool signalsBlocked() const
int startTimer(int interval, Qt::TimerType timerType = Qt::CoarseTimer)
QThread * thread() const
Public Slots
void deleteLater()
Signals
void destroyed(QObject *obj = Q_NULLPTR)
void objectNameChanged(const QString &objectName)
Static Public Members
QMetaObject::Connection connect(const QObject *sender, const char *signal, const QObject *receiver, const char *method, Qt::ConnectionType type = Qt::AutoConnection)
QMetaObject::Connection connect(const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type = Qt::AutoConnection)
QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method, Qt::ConnectionType type = Qt::AutoConnection)
QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, Functor functor)
QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, const QObject *context, Functor functor, Qt::ConnectionType type = Qt::AutoConnection)
bool disconnect(const QObject *sender, const char *signal, const QObject *receiver, const char *method)
bool disconnect(const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method)
bool disconnect(const QMetaObject::Connection &connection)
bool disconnect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method)
const QMetaObject staticMetaObject
QString tr()
Protected Functions
virtual void childEvent(QChildEvent *event)
virtual void connectNotify(const QMetaMethod &signal)
virtual void customEvent(QEvent *event)
virtual void disconnectNotify(const QMetaMethod &signal)
bool isSignalConnected(const QMetaMethod &signal) const
int receivers(const char *signal) const
QObject * sender() const
int senderSignalIndex() const
virtual void timerEvent(QTimerEvent *event)
Related Non-Members
typedef QObjectList
QList<T> qFindChildren(const QObject *obj, const QRegExp ®Exp)
T qobject_cast(QObject *object)
Macros
Q_CLASSINFO(Name, Value)
Q_DISABLE_COPY(Class)
Q_EMIT
Q_ENUM(...)
Q_FLAG(...)
Q_GADGET
Q_INTERFACES(...)
Q_INVOKABLE
Q_OBJECT
Q_PROPERTY(...)
Q_REVISION
Q_SET_OBJECT_NAME(Object)
Q_SIGNAL
Q_SIGNALS
Q_SLOT
Q_SLOTS
Detailed Description
The QObject class is the base class of all Qt objects.
QObject is the heart of the Qt Object Model. The central feature in this model is a very powerful mechanism for seamless object communication called signals and slots. You can connect a signal to a slot with connect() and destroy the connection with disconnect(). To avoid never ending notification loops you can temporarily block signals with blockSignals(). The protected functions connectNotify() and disconnectNotify() make it possible to track connections.
QObjects organize themselves in object trees. When you create a QObject with another object as parent, the object will automatically add itself to the parent's children() list. The parent takes ownership of the object; i.e., it will automatically delete its children in its destructor. You can look for an object by name and optionally type using findChild() or findChildren().
Every object has an objectName() and its class name can be found via the corresponding metaObject() (see QMetaObject::className()). You can determine whether the object's class inherits another class in the QObject inheritance hierarchy by using the inherits() function.
When an object is deleted, it emits a destroyed() signal. You can catch this signal to avoid dangling references to QObjects.
QObjects can receive events through event() and filter the events of other objects. See installEventFilter() and eventFilter() for details. A convenience handler, childEvent(), can be reimplemented to catch child events.
Last but not least, QObject provides the basic timer support in Qt; see QTimer for high-level support for timers.
Notice that the Q_OBJECT macro is mandatory for any object that implements signals, slots or properties. You also need to run the Meta Object Compiler on the source file. We strongly recommend the use of this macro in all subclasses of QObject regardless of whether or not they actually use signals, slots and properties, since failure to do so may lead certain functions to exhibit strange behavior.
All Qt widgets inherit QObject. The convenience function isWidgetType() returns whether an object is actually a widget. It is much faster than qobject_cast<QWidget *>(obj) or obj->inherits("QWidget").
Some QObject functions, e.g. children(), return a QObjectList. QObjectList is a typedef for QList<QObject *>.
Thread Affinity
A QObject instance is said to have a thread affinity, or that it lives in a certain thread. When a QObject receives a queued signal or a posted event, the slot or event handler will run in the thread that the object lives in.
Note: If a QObject has no thread affinity (that is, if thread() returns zero), or if it lives in a thread that has no running event loop, then it cannot receive queued signals or posted events.
By default, a QObject lives in the thread in which it is created. An object's thread affinity can be queried using thread() and changed using moveToThread().
All QObjects must live in the same thread as their parent. Consequently:
setParent() will fail if the two QObjects involved live in different threads.
When a QObject is moved to another thread, all its children will be automatically moved too.
moveToThread() will fail if the QObject has a parent.
If QObjects are created within QThread::run(), they cannot become children of the QThread object because the QThread does not live in the thread that calls QThread::run().
Note: A QObject's member variables do not automatically become its children. The parent-child relationship must be set by either passing a pointer to the child's constructor, or by calling setParent(). Without this step, the object's member variables will remain in the old thread when moveToThread() is called.
No Copy Constructor or Assignment Operator
QObject has neither a copy constructor nor an assignment operator. This is by design. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). In fact, all Qt classes derived from QObject (direct or indirect) use this macro to declare their copy constructor and assignment operator to be private. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page.
The main consequence is that you should use pointers to QObject (or to your QObject subclass) where you might otherwise be tempted to use your QObject subclass as a value. For example, without a copy constructor, you can't use a subclass of QObject as the value to be stored in one of the container classes. You must store pointers.
Auto-Connection
Qt's meta-object system provides a mechanism to automatically connect signals and slots between QObject subclasses and their children. As long as objects are defined with suitable object names, and slots follow a simple naming convention, this connection can be performed at run-time by the QMetaObject::connectSlotsByName() function.
uic generates code that invokes this function to enable auto-connection to be performed between widgets on forms created with Qt Designer. More information about using auto-connection with Qt Designer is given in the Using a Designer UI File in Your Application section of the Qt Designer manual.
Dynamic Properties
From Qt 4.2, dynamic properties can be added to and removed from QObject instances at run-time. Dynamic properties do not need to be declared at compile-time, yet they provide the same advantages as static properties and are manipulated using the same API - using property() to read them and setProperty() to write them.
From Qt 4.3, dynamic properties are supported by Qt Designer, and both standard Qt widgets and user-created forms can be given dynamic properties.
Internationalization (I18n)
All QObject subclasses support Qt's translation features, making it possible to translate an application's user interface into different languages.
To make user-visible text translatable, it must be wrapped in calls to the tr() function. This is explained in detail in the Writing Source Code for Translation document.
See also QMetaObject, QPointer, QObjectCleanupHandler, Q_DISABLE_COPY(), and Object Trees & Ownership.
Property Documentation
objectName : QString
This property holds the name of this object.
You can find an object by name (and type) using findChild(). You can find a set of objects with findChildren().
qDebug("MyClass::setPrecision(): (%s) invalid precision %f",
qPrintable(objectName()), newPrecision);
By default, this property contains an empty string.
Access functions:
QString objectName() const
void setObjectName(const QString &name)
Notifier signal:
void objectNameChanged(const QString &objectName) [see note below]
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
See also metaObject() and QMetaObject::className().
Member Function Documentation
QObject::QObject(QObject *parent = Q_NULLPTR)
Constructs an object with parent object parent.
The parent of an object may be viewed as the object's owner. For instance, a dialog box is the parent of the OK and Cancel buttons it contains.
The destructor of a parent object destroys all child objects.
Setting parent to constructs an object with no parent. If the object is a widget, it will become a top-level window.
See also parent(), findChild(), and findChildren().
[virtual] QObject::~QObject()
Destroys the object, deleting all its child objects.
All signals to and from the object are automatically disconnected, and any pending posted events for the object are removed from the event queue. However, it is often safer to use deleteLater() rather than deleting a QObject subclass directly.
Warning: All child objects are deleted. If any of these objects are on the stack or global, sooner or later your program will crash. We do not recommend holding pointers to child objects from outside the parent. If you still do, the destroyed() signal gives you an opportunity to detect when an object is destroyed.
Warning: Deleting a QObject while pending events are waiting to be delivered can cause a crash. You must not delete the QObject directly if it exists in a different thread than the one currently executing. Use deleteLater() instead, which will cause the event loop to delete the object after all pending events have been delivered to it.
See also deleteLater().
bool QObject::blockSignals(bool block)
If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). If block is false, no such blocking will occur.
The return value is the previous value of signalsBlocked().
Note that the destroyed() signal will be emitted even if the signals for this object have been blocked.
Signals emitted while being blocked are not buffered.
See also signalsBlocked() and QSignalBlocker.
[virtual protected] void QObject::childEvent(QChildEvent *event)
This event handler can be reimplemented in a subclass to receive child events. The event is passed in the event parameter.
QEvent::ChildAdded and QEvent::ChildRemoved events are sent to objects when children are added or removed. In both cases you can only rely on the child being a QObject, or if isWidgetType() returns true, a QWidget. (This is because, in the ChildAdded case, the child is not yet fully constructed, and in the ChildRemoved case it might have been destructed already).
QEvent::ChildPolished events are sent to widgets when children are polished, or when polished children are added. If you receive a child polished event, the child's construction is usually completed. However, this is not guaranteed, and multiple polish events may be delivered during the execution of a widget's constructor.
For every child widget, you receive one ChildAdded event, zero or more ChildPolished events, and one ChildRemoved event.
The ChildPolished event is omitted if a child is removed immediately after it is added. If a child is polished several times during construction and destruction, you may receive several child polished events for the same child, each time with a different virtual table.
See also event().
const QObjectList &QObject::children() const
Returns a list of child objects. The QObjectList class is defined in the <QObject> header file as the following:
typedef QList<QObject*> QObjectList;
The first child added is the first object in the list and the last child added is the last object in the list, i.e. new children are appended at the end.
Note that the list order changes when QWidget children are raised or lowered. A widget that is raised becomes the last object in the list, and a widget that is lowered becomes the first object in the list.
See also findChild(), findChildren(), parent(), and setParent().
[static] QMetaObject::Connection QObject::connect(const QObject *sender, const char *signal, const QObject *receiver, const char *method, Qt::ConnectionType type = Qt::AutoConnection)
Creates a connection of the given type from the signal in the sender object to the method in the receiver object. Returns a handle to the connection that can be used to disconnect it later.
You must use the SIGNAL() and SLOT() macros when specifying the signal and the method, for example:
QLabel *label = new QLabel;
QScrollBar *scrollBar = new QScrollBar;
QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
label, SLOT(setNum(int)));
This example ensures that the label always displays the current scroll bar value. Note that the signal and slots parameters must not contain any variable names, only the type. E.g. the following would not work and return false:
// WRONG
QObject::connect(scrollBar, SIGNAL(valueChanged(int value)),
label, SLOT(setNum(int value)));
A signal can also be connected to another signal:
class MyWidget : public QWidget
{
Q_OBJECT
public:
MyWidget();
signals:
void buttonClicked();
private:
QPushButton *myButton;
};
MyWidget::MyWidget()
{
myButton = new QPushButton(this);
connect(myButton, SIGNAL(clicked()),
this, SIGNAL(buttonClicked()));
}
In this example, the MyWidget constructor relays a signal from a private member variable, and makes it available under a name that relates to MyWidget.
A signal can be connected to many slots and signals. Many signals can be connected to one slot.
If a signal is connected to several slots, the slots are activated in the same order in which the connections were made, when the signal is emitted.
The function returns a QMetaObject::Connection that represents a handle to a connection if it successfully connects the signal to the slot. The connection handle will be invalid if it cannot create the connection, for example, if QObject is unable to verify the existence of either signal or method, or if their signatures aren't compatible. You can check if the handle is valid by casting it to a bool.
By default, a signal is emitted for every connection you make; two signals are emitted for duplicate connections. You can break all of these connections with a single disconnect() call. If you pass the Qt::UniqueConnection type, the connection will only be made if it is not a duplicate. If there is already a duplicate (exact same signal to the exact same slot on the same objects), the connection will fail and connect will return an invalid QMetaObject::Connection.
The optional type parameter describes the type of connection to establish. In particular, it determines whether a particular signal is delivered to a slot immediately or queued for delivery at a later time. If the signal is queued, the parameters must be of types that are known to Qt's meta-object system, because Qt needs to copy the arguments to store them in an event behind the scenes. If you try to use a queued connection and get the error message
QObject::connect: Cannot queue arguments of type 'MyType'
(Make sure 'MyType' is registered using qRegisterMetaType().)
call qRegisterMetaType() to register the data type before you establish the connection.
Note: This function is thread-safe
See also disconnect(), sender(), qRegisterMetaType(), and Q_DECLARE_METATYPE().
[static] QMetaObject::Connection QObject::connect(const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type = Qt::AutoConnection)
Creates a connection of the given type from the signal in the sender object to the method in the receiver object. Returns a handle to the connection that can be used to disconnect it later.
The Connection handle will be invalid if it cannot create the connection, for example, the parameters were invalid. You can check if the QMetaObject::Connection is valid by casting it to a bool.
This function works in the same way as connect(const QObject *sender, const char *signal, const QObject *receiver, const char *method, Qt::ConnectionType type) but it uses QMetaMethod to specify signal and method.
This function was introduced in Qt 4.8.
See also connect(const QObject *sender, const char *signal, const QObject *receiver, const char *method, Qt::ConnectionType type).
QMetaObject::Connection QObject::connect(const QObject *sender, const char *signal, const char *method, Qt::ConnectionType type = Qt::AutoConnection) const
This function overloads connect().
Connects signal from the sender object to this object's method.
Equivalent to connect(sender, signal, this, method, type).
Every connection you make emits a signal, so duplicate connections emit two signals. You can break a connection using disconnect().
Note: This function is thread-safe
See also disconnect().
[static] QMetaObject::Connection QObject::connect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method, Qt::ConnectionType type = Qt::AutoConnection)
This function overloads connect().
Creates a connection of the given type from the signal in the sender object to the method in the receiver object. Returns a handle to the connection that can be used to disconnect it later.
The signal must be a function declared as a signal in the header. The slot function can be any member function that can be connected to the signal. A slot can be connected to a given signal if the signal has at least as many arguments as the slot, and there is an implicit conversion between the types of the corresponding arguments in the signal and the slot.
Example:
QLabel *label = new QLabel;
QLineEdit *lineEdit = new QLineEdit;
QObject::connect(lineEdit, &QLineEdit::textChanged,
label, &QLabel::setText);
This example ensures that the label always displays the current line edit text.
A signal can be connected to many slots and signals. Many signals can be connected to one slot.
If a signal is connected to several slots, the slots are activated in the same order as the order the connection was made, when the signal is emitted
The function returns an handle to a connection if it successfully connects the signal to the slot. The Connection handle will be invalid if it cannot create the connection, for example, if QObject is unable to verify the existence of signal (if it was not declared as a signal) You can check if the QMetaObject::Connection is valid by casting it to a bool.
By default, a signal is emitted for every connection you make; two signals are emitted for duplicate connections. You can break all of these connections with a single disconnect() call. If you pass the Qt::UniqueConnection type, the connection will only be made if it is not a duplicate. If there is already a duplicate (exact same signal to the exact same slot on the same objects), the connection will fail and connect will return an invalid QMetaObject::Connection.
The optional type parameter describes the type of connection to establish. In particular, it determines whether a particular signal is delivered to a slot immediately or queued for delivery at a later time. If the signal is queued, the parameters must be of types that are known to Qt's meta-object system, because Qt needs to copy the arguments to store them in an event behind the scenes. If you try to use a queued connection and get the error message
QObject::connect: Cannot queue arguments of type 'MyType'
(Make sure 'MyType' is registered using qRegisterMetaType().)
make sure to declare the argument type with Q_DECLARE_METATYPE
Overloaded functions can be resolved with help of qOverload.
Note: The number of arguments variadic templates.
Note: This function is thread-safe
[static] QMetaObject::Connection QObject::connect(const QObject *sender, PointerToMemberFunction signal, Functor functor)
This function overloads connect().
Creates a connection from signal in sender object to functor, and returns a handle to the connection
The signal must be a function declared as a signal in the header. The slot function can be any function or functor that can be connected to the signal. A function can be connected to a given signal if the signal as at least as many argument as the slot. A functor can be connected to a signal if they have exactly the same number of arguments. There must exist implicit conversion between the types of the corresponding arguments in the signal and the slot.
Example:
void someFunction();
QPushButton *button = new QPushButton;
QObject::connect(button, &QPushButton::clicked, someFunction);
If your compiler support C++ lambda expressions, you can use them:
QByteArray page = ...;
QTcpSocket *socket = new QTcpSocket;
socket->connectToHost();
QObject::connect(socket, &QTcpSocket::connected, [=] () {
socket->write("GET " + page + "\r\n");
});
The connection will automatically disconnect if the sender is destroyed. However, you should take care that any objects used within the functor are still alive when the signal is emitted.
Overloaded functions can be resolved with help of qOverload.
Note: If the compiler does not support C++ variadic templates, the number of arguments , and the functor object must not have an overloaded or templated operator().
Note: This function is thread-safe
[static] QMetaObject::Connection QObject::connect(const QObject *sender, PointerToMemberFunction signal, const QObject *context, Functor functor, Qt::ConnectionType type = Qt::AutoConnection)
This function overloads connect().
Creates a connection of a given type from signal in sender object to functor to be placed in a specific event loop of context, and returns a handle to the connection
The signal must be a function declared as a signal in the header. The slot function can be any function or functor that can be connected to the signal. A function can be connected to a given signal if the signal as at least as many argument as the slot. A functor can be connected to a signal if they have exactly the same number of arguments. There must exist implicit conversion between the types of the corresponding arguments in the signal and the slot.
Example:
void someFunction();
QPushButton *button = new QPushButton;
QObject::connect(button, &QPushButton::clicked, this, someFunction, Qt::QueuedConnection);
If your compiler support C++ lambda expressions, you can use them:
QByteArray page = ...;
QTcpSocket *socket = new QTcpSocket;
socket->connectToHost();
QObject::connect(socket, &QTcpSocket::connected, this, [=] () {
socket->write("GET " + page + "\r\n");
}, Qt::AutoConnection);
The connection will automatically disconnect if the sender or the context is destroyed. However, you should take care that any objects used within the functor are still alive when the signal is emitted.
Overloaded functions can be resolved with help of qOverload.
Note: If the compiler does not support C++ variadic templates, the number of arguments , and the functor object must not have an overloaded or templated operator().
Note: This function is thread-safe
This function was introduced in Qt 5.2.
[virtual protected] void QObject::connectNotify(const QMetaMethod &signal)
This virtual function is called when something has been connected to signal in this object.
If you want to compare signal with a specific signal, you can use QMetaMethod::fromSignal() as follows:
if (signal == QMetaMethod::fromSignal(&MyObject::valueChanged)) {
// signal is valueChanged
}
Warning: This function violates the object-oriented principle of modularity. However, it might be useful when you need to perform expensive initialization only if something is connected to a signal.
Warning: This function is called from the thread which performs the connection, which may be a different thread from the thread in which this object lives.
This function was introduced in Qt 5.0.
See also connect() and disconnectNotify().
[virtual protected] void QObject::customEvent(QEvent *event)
This event handler can be reimplemented in a subclass to receive custom events. Custom events are user-defined events with a type value at least as large as the QEvent::User item of the QEvent::Type enum, and is typically a QEvent subclass. The event is passed in the event parameter.
See also event() and QEvent.
[slot] void QObject::deleteLater()
Schedules this object for deletion.
The object will be deleted when control returns to the event loop. If the event loop is not running when this function is called (e.g. deleteLater() is called on an object before QCoreApplication::exec()), the object will be deleted once the event loop is started. If deleteLater() is called after the main event loop has stopped, the object will not be deleted. Since Qt 4.8, if deleteLater() is called on an object that lives in a thread with no running event loop, the object will be destroyed when the thread finishes.
Note that entering and leaving a new event loop (e.g., by opening a modal dialog) will not perform the deferred deletion; for the object to be deleted, the control must return to the event loop from which deleteLater() was called.
Note: It is safe to call this function more than once; when the first deferred deletion event is delivered, any pending events for the object are removed from the event queue.
See also destroyed() and QPointer.
[signal] void QObject::destroyed(QObject *obj = Q_NULLPTR)
This signal is emitted immediately before the object obj is destroyed, and can not be blocked.
All the objects's children are destroyed immediately after this signal is emitted.
See also deleteLater() and QPointer.
[static] bool QObject::disconnect(const QObject *sender, const char *signal, const QObject *receiver, const char *method)
Disconnects signal in object sender from method in object receiver. Returns true if the connection is successfully broken; otherwise returns false.
A signal-slot connection is removed when either of the objects involved are destroyed.
disconnect() is typically used in three ways, as the following examples demonstrate.
Disconnect everything connected to an object's signals:
disconnect(myObject, , , );
equivalent to the non-static overloaded function
myObject->disconnect();
Disconnect everything connected to a specific signal:
disconnect(myObject, SIGNAL(mySignal()), , );
equivalent to the non-static overloaded function
myObject->disconnect(SIGNAL(mySignal()));
Disconnect a specific receiver:
disconnect(myObject, , myReceiver, );
equivalent to the non-static overloaded function
myObject->disconnect(myReceiver);
may be used as a wildcard, meaning "any signal", "any receiving object", or "any slot in the receiving object", respectively.
The sender may never be . (You cannot disconnect signals from more than one object in a single call.)
If signal , it disconnects receiver and method from any signal. If not, only the specified signal is disconnected.
If receiver , it disconnects anything connected to signal. If not, slots in objects other than receiver are not disconnected.
If method , it disconnects anything that if receiver is left out, so you cannot disconnect a specifically-named slot on all objects.
Note: This function is thread-safe
See also connect().
[static] bool QObject::disconnect(const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method)
Disconnects signal in object sender from method in object receiver. Returns true if the connection is successfully broken; otherwise returns false.
This function provides the same possibilities like disconnect(const QObject *sender, const char *signal, const QObject *receiver, const char *method) but uses QMetaMethod to represent the signal and the method to be disconnected.
Additionally this function returnsfalse and no signals and slots disconnected if:
signal is not a member of sender class or one of its parent classes.
method is not a member of receiver class or one of its parent classes.
signal instance represents not a signal.
QMetaMethod() may be used can be used .
This function was introduced in Qt 4.8.
See also disconnect(const QObject *sender, const char *signal, const QObject *receiver, const char *method).
bool QObject::disconnect(const char *signal = Q_NULLPTR, const QObject *receiver = Q_NULLPTR, const char *method = Q_NULLPTR) const
This function overloads disconnect().
Disconnects signal from method of receiver.
A signal-slot connection is removed when either of the objects involved are destroyed.
Note: This function is thread-safe
bool QObject::disconnect(const QObject *receiver, const char *method = Q_NULLPTR) const
This function overloads disconnect().
Disconnects all signals in this object from receiver's method.
A signal-slot connection is removed when either of the objects involved are destroyed.
[static] bool QObject::disconnect(const QMetaObject::Connection &connection)
Disconnect a connection.
If the connection is invalid or has already been disconnected, do nothing and return false.
See also connect().
[static] bool QObject::disconnect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method)
This function overloads diconnect().
Disconnects signal in object sender from method in object receiver. Returns true if the connection is successfully broken; otherwise returns false.
A signal-slot connection is removed when either of the objects involved are destroyed.
disconnect() is typically used in three ways, as the following examples demonstrate.
Disconnect everything connected to an object's signals:
disconnect(myObject, , , );
Disconnect everything connected to a specific signal:
disconnect(myObject, &MyObject::mySignal(), , );
Disconnect a specific receiver:
disconnect(myObject, , myReceiver, );
Disconnect a connection from one specific signal to a specific slot:
QObject::disconnect(lineEdit, &QLineEdit::textChanged,
label, &QLabel::setText);
may be used as a wildcard, meaning "any signal", "any receiving object", or "any slot in the receiving object", respectively.
The sender may never be . (You cannot disconnect signals from more than one object in a single call.)
If signal , it disconnects receiver and method from any signal. If not, only the specified signal is disconnected.
If receiver , it disconnects anything connected to signal. If not, slots in objects other than receiver are not disconnected.
If method , it disconnects anything that if receiver is left out, so you cannot disconnect a specifically-named slot on all objects.
Note: It is not possible to use this overload to diconnect signals connected to functors or lambda expressions. That is because it is not possible to compare them. Instead, use the overload that takes a QMetaObject::Connection
Note: This function is thread-safe
See also connect().
[virtual protected] void QObject::disconnectNotify(const QMetaMethod &signal)
This virtual function is called when something has been disconnected from signal in this object.
See connectNotify() for an example of how to compare signal with a specific signal.
If all signals were disconnected ), disconnectNotify() is only called once, and the signal will be an invalid QMetaMethod (QMetaMethod::isValid() returns false).
Warning: This function violates the object-oriented principle of modularity. However, it might be useful for optimizing access to expensive resources.
Warning: This function is called from the thread which performs the disconnection, which may be a different thread from the thread in which this object lives. This function may also be called with a QObject internal mutex locked. It is therefore not allowed to re-enter any of any QObject functions from your reimplementation and if you lock a mutex in your reimplementation, make sure that you don't call QObject functions with that mutex held in other places or it will result in a deadlock.
This function was introduced in Qt 5.0.
See also disconnect() and connectNotify().
void QObject::dumpObjectInfo()
Dumps information about signal connections, etc. for this object to the debug output.
This function is useful for debugging, but does nothing if the library has been compiled in release mode (i.e. without debugging information).
See also dumpObjectTree().
void QObject::dumpObjectTree()
Dumps a tree of children to the debug output.
This function is useful for debugging, but does nothing if the library has been compiled in release mode (i.e. without debugging information).
See also dumpObjectInfo().
QList<QByteArray> QObject::dynamicPropertyNames() const
Returns the names of all properties that were dynamically added to the object using setProperty().
This function was introduced in Qt 4.2.
[virtual] bool QObject::event(QEvent *e)
This virtual function receives events to an object and should return true if the event e was recognized and processed.
The event() function can be reimplemented to customize the behavior of an object.
Make sure you call the parent event class implementation for all the events you did not handle.
Example:
class MyClass : public QWidget
{
Q_OBJECT
public:
MyClass(QWidget *parent = );
~MyClass();
bool event(QEvent* ev)
{
if (ev->type() == QEvent::PolishRequest) {
// overwrite handling of PolishRequest if any
doThings();
return true;
} else if (ev->type() == QEvent::Show) {
// complement handling of Show if any
doThings2();
QWidget::event(ev);
return true;
}
// Make sure the rest of events are handled
return QWidget::event(ev);
}
};
See also installEventFilter(), timerEvent(), QCoreApplication::sendEvent(), and QCoreApplication::postEvent().
[virtual] bool QObject::eventFilter(QObject *watched, QEvent *event)
Filters events if this object has been installed as an event filter for the watched object.
In your reimplementation of this function, if you want to filter the event out, i.e. stop it being handled further, return true; otherwise return false.
Example:
class MainWindow : public QMainWindow
{
public:
MainWindow();
protected:
bool eventFilter(QObject *obj, QEvent *ev);
private:
QTextEdit *textEdit;
};
MainWindow::MainWindow()
{
textEdit = new QTextEdit;
setCentralWidget(textEdit);
textEdit->installEventFilter(this);
}
bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
if (obj == textEdit) {
if (event->type() == QEvent::KeyPress) {
QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
qDebug() << "Ate key press" << keyEvent->key();
return true;
} else {
return false;
}
} else {
// pass the event on to the parent class
return QMainWindow::eventFilter(obj, event);
}
}
Notice in the example above that unhandled events are passed to the base class's eventFilter() function, since the base class might have reimplemented eventFilter() for its own internal purposes.
Warning: If you delete the receiver object in this function, be sure to return true. Otherwise, Qt will forward the event to the deleted object and the program might crash.
See also installEventFilter().
T QObject::findChild(const QString &name = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
Returns the child of if there is no such object. Omitting the name argument causes all object names to be matched. The search is performed recursively, unless options specifies the option FindDirectChildrenOnly.
If there is more than one child matching the search, the most direct ancestor is returned. If there are several direct ancestors, it is undefined which one will be returned. In that case, findChildren() should be used.
This example returns a child QPushButton of parentWidget named "button1", even if the button isn't a direct child of the parent:
QPushButton *button = parentWidget->findChild<QPushButton *>("button1");
This example returns a QListWidget child of parentWidget:
QListWidget *list = parentWidget->findChild<QListWidget *>();
This example returns a child QPushButton of parentWidget (its direct parent) named "button1":
QPushButton *button = parentWidget->findChild<QPushButton *>("button1", Qt::FindDirectChildrenOnly);
This example returns a QListWidget child of parentWidget, its direct parent:
QListWidget *list = parentWidget->findChild<QListWidget *>(QString(), Qt::FindDirectChildrenOnly);
See also findChildren().
QList<T> QObject::findChildren(const QString &name = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. Omitting the name argument causes all object names to be matched. The search is performed recursively, unless options specifies the option FindDirectChildrenOnly.
The following example shows how to find a list of child QWidgets of the specified parentWidget named widgetname:
QList<QWidget *> widgets = parentWidget.findChildren<QWidget *>("widgetname");
This example returns all QPushButtons that are children of parentWidget:
QList<QPushButton *> allPButtons = parentWidget.findChildren<QPushButton *>();
This example returns all QPushButtons that are immediate children of parentWidget:
QList<QPushButton *> childButtons = parentWidget.findChildren<QPushButton *>(QString(), Qt::FindDirectChildrenOnly);
See also findChild().
QList<T> QObject::findChildren(const QRegExp ®Exp, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
This function overloads findChildren().
Returns the children of this object that can be cast to type T and that have names matching the regular expression regExp, or an empty list if there are no such objects. The search is performed recursively, unless options specifies the option FindDirectChildrenOnly.
QList<T> QObject::findChildren(const QRegularExpression &re, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
This function overloads findChildren().
Returns the children of this object that can be cast to type T and that have names matching the regular expression re, or an empty list if there are no such objects. The search is performed recursively, unless options specifies the option FindDirectChildrenOnly.
This function was introduced in Qt 5.0.
bool QObject::inherits(const char *className) const
Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false.
A class is considered to inherit itself.
Example:
QTimer *timer = new QTimer; // QTimer inherits QObject
timer->inherits("QTimer"); // returns true
timer->inherits("QObject"); // returns true
timer->inherits("QAbstractButton"); // returns false
// QVBoxLayout inherits QObject and QLayoutItem
QVBoxLayout *layout = new QVBoxLayout;
layout->inherits("QObject"); // returns true
layout->inherits("QLayoutItem"); // returns true (even though QLayoutItem is not a QObject)
If you need to determine whether an object is an instance of a particular class for the purpose of casting it, consider using qobject_cast<Type *>(object) instead.
See also metaObject() and qobject_cast().
void QObject::installEventFilter(QObject *filterObj)
Installs an event filter filterObj on this object. For example:
monitoredObj->installEventFilter(filterObj);
An event filter is an object that receives all events that are sent to this object. The filter can either stop the event or forward it to this object. The event filter filterObj receives events via its eventFilter() function. The eventFilter() function must return true if the event should be filtered, (i.e. stopped); otherwise it must return false.
If multiple event filters are installed on a single object, the filter that was installed last is activated first.
Here's a KeyPressEater class that eats the key presses of its monitored objects:
class KeyPressEater : public QObject
{
Q_OBJECT
...
protected:
bool eventFilter(QObject *obj, QEvent *event);
};
bool KeyPressEater::eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::KeyPress) {
QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
qDebug("Ate key press %d", keyEvent->key());
return true;
} else {
// standard event processing
return QObject::eventFilter(obj, event);
}
}
And here's how to install it on two widgets:
KeyPressEater *keyPressEater = new KeyPressEater(this);
QPushButton *pushButton = new QPushButton(this);
QListView *listView = new QListView(this);
pushButton->installEventFilter(keyPressEater);
listView->installEventFilter(keyPressEater);
The QShortcut class, for example, uses this technique to intercept shortcut key presses.
Warning: If you delete the receiver object in your eventFilter() function, be sure to return true. If you return false, Qt sends the event to the deleted object and the program will crash.
Note that the filtering object must be in the same thread as this object. If filterObj is in a different thread, this function does nothing. If either filterObj or this object are moved to a different thread after calling this function, the event filter will not be called until both objects have the same thread affinity again (it is not removed).
See also removeEventFilter(), eventFilter(), and event().
[protected] bool QObject::isSignalConnected(const QMetaMethod &signal) const
Returns true if the signal is connected to at least one receiver, otherwise returns false.
signal must be a signal member of this object, otherwise the behaviour is undefined.
static const QMetaMethod valueChangedSignal = QMetaMethod::fromSignal(&MyObject::valueChanged);
if (isSignalConnected(valueChangedSignal)) {
QByteArray data;
data = get_the_value(); // expensive operation
emit valueChanged(data);
}
As the code snippet above illustrates, you can use this function to avoid emitting a signal that nobody listens to.
Warning: This function violates the object-oriented principle of modularity. However, it might be useful when you need to perform expensive initialization only if something is connected to a signal.
This function was introduced in Qt 5.0.
bool QObject::isWidgetType() const
Returns true if the object is a widget; otherwise returns false.
Calling this function is equivalent to calling inherits("QWidget"), except that it is much faster.
bool QObject::isWindowType() const
Returns true if the object is a window; otherwise returns false.
Calling this function is equivalent to calling inherits("QWindow"), except that it is much faster.
void QObject::killTimer(int id)
Kills the timer with timer identifier, id.
The timer identifier is returned by startTimer() when a timer event is started.
See also timerEvent() and startTimer().
[virtual] const QMetaObject *QObject::metaObject() const
Returns a pointer to the meta-object of this object.
A meta-object contains information about a class that inherits QObject, e.g. class name, superclass name, properties, signals and slots. Every QObject subclass that contains the Q_OBJECT macro will have a meta-object.
The meta-object information is required by the signal/slot connection mechanism and the property system. The inherits() function also makes use of the meta-object.
If you have no pointer to an actual object instance but still want to access the meta-object of a class, you can use staticMetaObject.
Example:
QObject *obj = new QPushButton;
obj->metaObject()->className(); // returns "QPushButton"
QPushButton::staticMetaObject.className(); // returns "QPushButton"
See also staticMetaObject.
void QObject::moveToThread(QThread *targetThread)
Changes the thread affinity for this object and its children. The object cannot be moved if it has a parent. Event processing will continue in the targetThread.
To move an object to the main thread, use QApplication::instance() to retrieve a pointer to the current application, and then use QApplication::thread() to retrieve the thread in which the application lives. For example:
myObject->moveToThread(QApplication::instance()->thread());
If targetThread is zero, all event processing for this object and its children stops.
Note that all active timers for the object will be reset. The timers are first stopped in the current thread and restarted (with the same interval) in the targetThread. As a result, constantly moving an object between threads can postpone timer events indefinitely.
A QEvent::ThreadChange event is sent to this object just before the thread affinity is changed. You can handle this event to perform any special processing. Note that any new events that are posted to this object will be handled in the targetThread.
Warning: This function is not thread-safe; the current thread must be same as the current thread affinity. In other words, this function can only "push" an object from the current thread to another thread, it cannot "pull" an object from any arbitrary thread to the current thread.
See also thread().
[signal] void QObject::objectNameChanged(const QString &objectName)
This signal is emitted after the object's name has been changed. The new object name is passed as objectName.
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
Note: Notifier signal for property objectName.
See also QObject::objectName.
QObject *QObject::parent() const
Returns a pointer to the parent object.
See also setParent() and children().
QVariant QObject::property(const char *name) const
Returns the value of the object's name property.
If no such property exists, the returned variant is invalid.
Information about all available properties is provided through the metaObject() and dynamicPropertyNames().
See also setProperty(), QVariant::isValid(), metaObject(), and dynamicPropertyNames().
[protected] int QObject::receivers(const char *signal) const
Returns the number of receivers connected to the signal.
Since both slots and signals can be used as receivers for signals, and the same connections can be made many times, the number of receivers is the same as the number of connections made from this signal.
When calling this function, you can use the SIGNAL() macro to pass a specific signal:
) {
QByteArray data;
get_the_value(&data); // expensive operation
emit valueChanged(data);
}
Warning: This function violates the object-oriented principle of modularity. However, it might be useful when you need to perform expensive initialization only if something is connected to a signal.
See also isSignalConnected().
void QObject::removeEventFilter(QObject *obj)
Removes an event filter object obj from this object. The request is ignored if such an event filter has not been installed.
All event filters for this object are automatically removed when this object is destroyed.
It is always safe to remove an event filter, even during event filter activation (i.e. from the eventFilter() function).
See also installEventFilter(), eventFilter(), and event().
[protected] QObject *QObject::sender() const
Returns a pointer to the . The pointer is valid only during the execution of the slot that calls this function from this object's thread context.
The pointer returned by this function becomes invalid if the sender is destroyed, or if the slot is disconnected from the sender's signal.
Warning: This function violates the object-oriented principle of modularity. However, getting access to the sender might be useful when many signals are connected to a single slot.
Warning: As mentioned above, the return value of this function is not valid when the slot is called via a Qt::DirectConnection from a thread different from this object's thread. Do not use this function in this type of scenario.
See also senderSignalIndex() and QSignalMapper.
[protected] int QObject::senderSignalIndex() const
Returns the meta-method index of the signal that called the currently executing slot, which is returned.
For signals with ) will have two different indexes (with and without the parameter), but this function will always return the index with a parameter. This does not apply when overloading signals with different parameters.
Warning: This function violates the object-oriented principle of modularity. However, getting access to the signal index might be useful when many signals are connected to a single slot.
Warning: The return value of this function is not valid when the slot is called via a Qt::DirectConnection from a thread different from this object's thread. Do not use this function in this type of scenario.
This function was introduced in Qt 4.8.
See also sender(), QMetaObject::indexOfSignal(), and QMetaObject::method().
void QObject::setParent(QObject *parent)
Makes the object a child of parent.
See also parent() and children().
bool QObject::setProperty(const char *name, const QVariant &value)
Sets the value of the object's name property to value.
If the property is defined in the class using Q_PROPERTY then true is returned on success and false otherwise. If the property is not defined using Q_PROPERTY, and therefore not listed in the meta-object, it is added as a dynamic property and false is returned.
Information about all available properties is provided through the metaObject() and dynamicPropertyNames().
Dynamic properties can be queried again using property() and can be removed by setting the property value to an invalid QVariant. Changing the value of a dynamic property causes a QDynamicPropertyChangeEvent to be sent to the object.
Note: Dynamic properties starting with "_q_" are reserved for internal purposes.
See also property(), metaObject(), dynamicPropertyNames(), and QMetaProperty::write().
bool QObject::signalsBlocked() const
Returns true if signals are blocked; otherwise returns false.
Signals are not blocked by default.
See also blockSignals() and QSignalBlocker.
int QObject::startTimer(int interval, Qt::TimerType timerType = Qt::CoarseTimer)
Starts a timer and returns a timer identifier, or returns zero if it could not start a timer.
A timer , then the timer event occurs once every time there are no more window system events to process.
The virtual timerEvent() function is called with the QTimerEvent event parameter class when a timer event occurs. Reimplement this function to get timer events.
If multiple timers are running, the QTimerEvent::timerId() can be used to find out which timer was activated.
Example:
class MyObject : public QObject
{
Q_OBJECT
public:
MyObject(QObject *parent = );
protected:
void timerEvent(QTimerEvent *event);
};
MyObject::MyObject(QObject *parent)
: QObject(parent)
{
startTimer(); // 50-millisecond timer
startTimer(); // 1-second timer
startTimer(); // 1-minute timer
}
void MyObject::timerEvent(QTimerEvent *event)
{
qDebug() << "Timer ID:" << event->timerId();
}
Note that QTimer's accuracy depends on the underlying operating system and hardware. The timerType argument allows you to customize the accuracy of the timer. See Qt::TimerType for information on the different timer types. Most platforms support an accuracy of 20 milliseconds; some provide more. If Qt is unable to deliver the requested number of timer events, it will silently discard some.
The QTimer class provides a high-level programming interface with single-shot timers and timer signals instead of events. There is also a QBasicTimer class that is more lightweight than QTimer and less clumsy than using timer IDs directly.
See also timerEvent(), killTimer(), and QTimer::singleShot().
QThread *QObject::thread() const
Returns the thread in which the object lives.
See also moveToThread().
[virtual protected] void QObject::timerEvent(QTimerEvent *event)
This event handler can be reimplemented in a subclass to receive timer events for the object.
QTimer provides a higher-level interface to the timer functionality, and also more general information about timers. The timer event is passed in the event parameter.
See also startTimer(), killTimer(), and event().
[)
Returns a translated version of sourceText, optionally based on a disambiguation string and value of n for strings containing plurals; otherwise returns QString::fromUtf8(sourceText) if no appropriate translated string is available.
Example:
void MainWindow::createActions()
{
QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
...
If the same sourceText by default). In Qt 4.4 and earlier, this was the preferred way to pass comments to translators.
Example:
MyWindow::MyWindow()
{
QLabel *senderLabel = new QLabel(tr("Name:"));
QLabel *recipientLabel = new QLabel(tr("Name:", "recipient"));
...
See Writing Source Code for Translation for a detailed description of Qt's translation mechanisms in general, and the Disambiguation section for information on disambiguation.
Warning: This method is reentrant only if all translators are installed before calling this method. Installing or removing translators while performing translations is not supported. Doing so will probably result in crashes or other undesirable behavior.
See also QCoreApplication::translate() and Internationalization with Qt.
Member Variable Documentation
const QMetaObject QObject::staticMetaObject
This variable stores the meta-object for the class.
A meta-object contains information about a class that inherits QObject, e.g. class name, superclass name, properties, signals and slots. Every class that contains the Q_OBJECT macro will also have a meta-object.
The meta-object information is required by the signal/slot connection mechanism and the property system. The inherits() function also makes use of the meta-object.
If you have a pointer to an object, you can use metaObject() to retrieve the meta-object associated with that object.
Example:
QPushButton::staticMetaObject.className(); // returns "QPushButton"
QObject *obj = new QPushButton;
obj->metaObject()->className(); // returns "QPushButton"
See also metaObject().
Related Non-Members
typedef QObjectList
Synonym for QList<QObject *>.
QList<T> qFindChildren(const QObject *obj, const QRegExp ®Exp)
This function overloads qFindChildren().
This function is equivalent to obj->findChildren<T>(regExp).
Note: This function was provided which did not support member template functions. It is advised to use the other form in new code.
See also QObject::findChildren().
T qobject_cast(QObject *object)
Returns the given . If then it will also .
The class T must inherit (directly or indirectly) QObject and be declared with the Q_OBJECT macro.
A class is considered to inherit itself.
Example:
QObject *obj = new QTimer; // QTimer inherits QObject
QTimer *timer = qobject_cast<QTimer *>(obj);
// timer == (QObject *)obj
QAbstractButton *button = qobject_cast<QAbstractButton *>(obj);
// button == 0
The qobject_cast() function behaves similarly to the standard C++ dynamic_cast(), with the advantages that it doesn't require RTTI support and it works across dynamic library boundaries.
qobject_cast() can also be used in conjunction with interfaces; see the Plug & Paint example for details.
Warning: If T isn't declared with the Q_OBJECT macro, this function's return value is undefined.
See also QObject::inherits().
Macro Documentation
Q_CLASSINFO(Name, Value)
This macro associates extra information to the class, which is available using QObject::metaObject(). Qt makes only limited use of this feature, in the Active Qt, Qt D-Bus and Qt QML.
The extra information takes the form of a Name string and a Value literal string.
Example:
class MyClass : public QObject
{
Q_OBJECT
Q_CLASSINFO("Author", "Pierre Gendron")
Q_CLASSINFO("URL", "http://www.my-organization.qc.ca")
public:
...
};
See also QMetaObject::classInfo(), QAxFactory, Using Qt D-Bus Adaptors, and Extending QML.
Q_DISABLE_COPY(Class)
Disables the use of copy constructors and assignment operators for the given Class.
Instances of subclasses of QObject should not be thought of as values that can be copied or assigned, but as unique identities. This means that when you create your own subclass of QObject (director or indirect), you should not give it a copy constructor or an assignment operator. However, it may not enough to simply omit them from your class, because, if you mistakenly write some code that requires a copy constructor or an assignment operator (it's easy to do), your compiler will thoughtfully create it for you. You must do more.
The curious user will have seen that the Qt classes derived from QObject typically include this macro in a private section:
class MyClass : public QObject
{
private:
Q_DISABLE_COPY(MyClass)
};
It declares a copy constructor and an assignment operator in the private section, so that if you use them by mistake, the compiler will report an error.
class MyClass : public QObject
{
private:
MyClass(const MyClass &);
MyClass &operator=(const MyClass &);
};
But even this might not catch absolutely every case. You might be tempted to do something like this:
QWidget w = QWidget();
First of all, don't do that. Most compilers will generate code that uses the copy constructor, so the privacy violation error will be reported, but your C++ compiler is not required to generate code for this statement in a specific way. It could generate code using neither the copy constructor nor the assignment operator we made private. In that case, no error would be reported, but your application would probably crash when you called a member function of w.
Q_EMIT
Use this macro to replace the emit keyword for emitting signals, when you want to use Qt Signals and Slots with a 3rd party signal/slot mechanism.
The macro is normally used when no_keywords is specified with the CONFIG variable in the .pro file, but it can be used even when no_keywords is not specified.
Q_ENUM(...)
This macro registers an enum type with the meta-object system. It must be placed after the enum declaration in a class that has the Q_OBJECT or the Q_GADGET macro.
For example:
class MyClass : public QObject
{
Q_OBJECT
public:
MyClass(QObject *parent = );
~MyClass();
enum Priority { High, Low, VeryHigh, VeryLow };
Q_ENUM(Priority)
void setPriority(Priority priority);
Priority priority() const;
};
Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. You can also use QMetaEnum::fromType() to get the QMetaEnum.
Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use Q_DECLARE_METATYPE(). This will enable useful features; for example, if used in a QVariant, you can convert them to strings. Likewise, passing them to QDebug will print out their names.
This function was introduced in Qt 5.5.
See also Qt's Property System.
Q_FLAG(...)
This macro registers a single flags types with the meta-object system. It is typically used in a class definition to declare that values of a given enum can be used as flags and combined using the bitwise OR operator.
The macro must be placed after the enum declaration.
For example, in QLibrary, the LoadHints flag is declared in the following way:
class QLibrary : public QObject
{
Q_OBJECT
public:
...
enum LoadHint {
ResolveAllSymbolsHint = 0x01,
ExportExternalSymbolsHint = 0x02,
LoadArchiveMemberHint = 0x04
};
Q_DECLARE_FLAGS(LoadHints, LoadHint)
Q_FLAG(LoadHints)
...
}
The declaration of the flags themselves is performed in the public section of the QLibrary class itself, using the Q_DECLARE_FLAGS() macro.
Note: The Q_FLAG macro takes care of registering individual flag values with the meta-object system, so it is unnecessary to use Q_ENUM() in addition to this macro.
This function was introduced in Qt 5.5.
See also Qt's Property System.
Q_GADGET
The Q_GADGET macro is a lighter version of the Q_OBJECT macro for classes that do not inherit from QObject but still want to use some of the reflection capabilities offered by QMetaObject. Just like the Q_OBJECT macro, it must appear in the private section of a class definition.
Q_GADGETs can have Q_ENUM, Q_PROPERTY and Q_INVOKABLE, but they cannot have signals or slots
Q_GADGET makes a class member, staticMetaObject, available. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS.
Q_INTERFACES(...)
This macro tells Qt which interfaces the class implements. This is used when implementing plugins.
Example:
class BasicToolsPlugin : public QObject,
public BrushInterface,
public ShapeInterface,
public FilterInterface
{
Q_OBJECT
Q_PLUGIN_METADATA(IID "org.qt-project.Qt.Examples.PlugAndPaint.BrushInterface" FILE "basictools.json")
Q_INTERFACES(BrushInterface ShapeInterface FilterInterface)
public:
...
};
See the Plug & Paint Basic Tools example for details.
See also Q_DECLARE_INTERFACE(), Q_PLUGIN_METADATA(), and How to Create Qt Plugins.
Q_INVOKABLE
Apply this macro to declarations of member functions to allow them to be invoked via the meta-object system. The macro is written before the return type, as shown in the following example:
class Window : public QWidget
{
Q_OBJECT
public:
Window();
void normalMethod();
Q_INVOKABLE void invokableMethod();
};
The invokableMethod() function is marked up using Q_INVOKABLE, causing it to be registered with the meta-object system and enabling it to be invoked using QMetaObject::invokeMethod(). Since normalMethod() function is not registered in this way, it cannot be invoked using QMetaObject::invokeMethod().
Q_OBJECT
The Q_OBJECT macro must appear in the private section of a class definition that declares its own signals and slots or that uses other services provided by Qt's meta-object system.
For example:
#include <QObject>
class Counter : public QObject
{
Q_OBJECT
public:
Counter() { m_value = ; }
int value() const { return m_value; }
public slots:
void setValue(int value);
signals:
void valueChanged(int newValue);
private:
int m_value;
};
Note: This macro requires the class to be a subclass of QObject. Use Q_GADGET instead of Q_OBJECT to enable the meta object system's support for enums in a class that is not a QObject subclass.
See also Meta-Object System, Signals and Slots, and Qt's Property System.
Q_PROPERTY(...)
This macro is used for declaring properties in classes that inherit QObject. Properties behave like class data members, but they have additional features accessible through the Meta-Object System.
Q_PROPERTY(type name
(READ getFunction [WRITE setFunction] |
MEMBER memberName [(READ getFunction | WRITE setFunction)])
[RESET resetFunction]
[NOTIFY notifySignal]
[REVISION int]
[DESIGNABLE bool]
[SCRIPTABLE bool]
[STORED bool]
[USER bool]
[CONSTANT]
[FINAL])
The property name and type and the READ function are required. The type can be any type supported by QVariant, or it can be a user-defined type. The other items are optional, but a WRITE function is common. The attributes default to true except USER, which defaults to false.
For example:
Q_PROPERTY(QString title READ title WRITE setTitle USER true)
For more details about how to use this macro, and a more detailed example of its use, see the discussion on Qt's Property System.
See also Qt's Property System.
Q_REVISION
Apply this macro to declarations of member functions to tag them with a revision number in the meta-object system. The macro is written before the return type, as shown in the following example:
class Window : public QWidget
{
Q_OBJECT
Q_PROPERTY(int normalProperty READ normalProperty)
Q_PROPERTY()
public:
Window();
int normalProperty();
int newProperty();
public slots:
void normalMethod();
Q_REVISION() void newMethod();
};
This is useful when using the meta-object system to dynamically expose objects to another API, as you can match the version expected by multiple versions of the other API. Consider the following simplified example:
Window window;
;
const QMetaObject *windowMetaObject = window.metaObject();
; i < windowMetaObject->methodCount(); i++)
if (windowMetaObject->method(i).revision() <= expectedRevision)
exposeMethod(windowMetaObject->method(i));
; i < windowMetaObject->propertyCount(); i++)
if (windowMetaObject->property(i).revision() <= expectedRevision)
exposeProperty(windowMetaObject->property(i));
Using the same Window or greater.
Since all methods are considered to be ) is invalid and ignored.
This tag is not used by the meta-object system itself. Currently this is only used by the QtQml module.
For a more generic string tag, see QMetaMethod::tag()
See also QMetaMethod::revision().
Q_SET_OBJECT_NAME(Object)
This macro assigns Object the objectName "Object".
It doesn't matter whether Object is a pointer or not, the macro figures that out by itself.
This function was introduced in Qt 5.0.
See also QObject::objectName().
Q_SIGNAL
This is an additional macro that allows you to mark a single function as a signal. It can be quite useful, especially when you use a 3rd-party source code parser which doesn't understand a signals or Q_SIGNALS groups.
Use this macro to replace the signals keyword in class declarations, when you want to use Qt Signals and Slots with a 3rd party signal/slot mechanism.
The macro is normally used when no_keywords is specified with the CONFIG variable in the .pro file, but it can be used even when no_keywords is not specified.
Q_SIGNALS
Use this macro to replace the signals keyword in class declarations, when you want to use Qt Signals and Slots with a 3rd party signal/slot mechanism.
The macro is normally used when no_keywords is specified with the CONFIG variable in the .pro file, but it can be used even when no_keywords is not specified.
Q_SLOT
This is an additional macro that allows you to mark a single function as a slot. It can be quite useful, especially when you use a 3rd-party source code parser which doesn't understand a slots or Q_SLOTS groups.
Use this macro to replace the slots keyword in class declarations, when you want to use Qt Signals and Slots with a 3rd party signal/slot mechanism.
The macro is normally used when no_keywords is specified with the CONFIG variable in the .pro file, but it can be used even when no_keywords is not specified.
Q_SLOTS
Use this macro to replace the slots keyword in class declarations, when you want to use Qt Signals and Slots with a 3rd party signal/slot mechanism.
The macro is normally used when no_keywords is specified with the CONFIG variable in the .pro file, but it can be used even when no_keywords is not specified.
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//337.out.txt -- 输出数据
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Reference<deque>deque
Not
logged
registerlog
template
:
<deque>
?
std::deque
<
T,
Alloc
=
allocator<T>
>
deque;
Double
ended
queue
deque
(usually
pronounced
like
an
irregular
acronym
of
queue.
Double-ended
queues
are
sequence
containers
with
dynamic
sizes
that
can
be
expanded
or
contracted
on
both
ends
(either
its
front
back).
Specific
libraries
may
implement
deques
different
ways,
generally
some
form
array.
But
any
they
allow
the
individual
elements
to
accessed
directly
through
random
access
iterators,
storage
handled
automatically
by
expanding
and
contracting
container
needed.
Therefore,
provide
a
functionality
similar
vectors,
but
efficient
insertion
deletion
also
at
beginning
sequence,
not
only
end.
But,
unlike
guaranteed
store
all
contiguous
locations:
accessing
offsetting
pointer
another
element
causes
undefined
behavior.
Both
vectors
very
used
purposes,
internally
work
quite
ways:
While
use
single
array
needs
occasionally
reallocated
growth,
scattered
chunks
storage,
keeping
necessary
information
direct
constant
time
uniform
sequential
(through
iterators).
little
more
complex
than
allows
them
grow
efficiently
under
certain
circumstances,
especially
sequences,
reallocations
become
expensive.
For
operations
involve
frequent
removals
positions
other
end,
perform
worse
have
less
consistent
iterators
references
lists
forward
lists.
Container
properties
Sequence
Elements
ordered
strict
linear
sequence.
Individual
their
position
Dynamic
Generally
implemented
array,
it
provides
relatively
fast
addition/removal
end
Allocator-aware
The
uses
allocator
dynamically
handle
needs.
Template
parameters
T
Type
elements.
Aliased
member
type
deque::value_type.
define
allocation
model.
By
used,
which
defines
simplest
memory
model
value-independent.
deque::allocator_type.
Member
types
C++98C++
definition
notes
value_type
first
parameter
(T)
allocator_type
second
(Alloc)
defaults
to:
allocator<value_type>
reference
allocator_type::reference
allocator:
value_type&
const_reference
allocator_type::const_reference
allocator_type::pointer
value_type*
const_pointer
allocator_type::const_pointer
iterator
convertible
const_iterator
reverse_iterator
reverse_iterator<iterator>
const_reverse_iterator
reverse_iterator<const_iterator>
difference_type
signed
integral
type,
identical
iterator_traits<iterator>::difference_type
usually
same
ptrdiff_t
size_type
unsigned
represent
non-negative
value
size_t
functions
(constructor)
Construct
(
function
)
(destructor)
Deque
destructor
Assign
content
Iterators:
begin
Return
rbegin
reverse
rend
cbegin
cend
crbegin
crend
Capacity:
size
max_size
maximum
resize
Change
empty
Test
whether
shrink_to_fit
Shrink
fit
Element
access:
Access
back
last
Modifiers:
assign
push_back
Add
push_front
Insert
pop_back
Delete
pop_front
insert
erase
Erase
swap
Swap
clear
Clear
emplace
emplace_front
emplace_back
Allocator:
get_allocator
Get
Non-member
overloads
relational
operators
Relational
(function
Exchanges
contents
two
C++
Information
Tutorials
Reference
Articles
Forum
C
library:
Containers:
<array>
<forward_list>
<list>
<map>
<queue>
<
<stack>
<unordered_map>
<unordered_set>
<vector>
Input/Output:
Multi-threading:
Other:
deque::deque
deque::~deque
functions:
deque::assign
deque::at
deque::back
deque::begin
deque::cbegin
deque::cend
deque::clear
deque::crbegin
deque::crend
deque::emplace
deque::emplace_back
deque::emplace_front
deque::empty
deque::end
deque::erase
deque::front
deque::get_allocator
deque::insert
deque::max_size
deque::
deque::
deque::pop_back
deque::pop_front
deque::push_back
deque::push_front
deque::rbegin
deque::rend
deque::resize
deque::shrink_to_fit
deque::size
deque::swap
non-member
overloads:
(deque)
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following
table
incorporate
well
modules
license
license.
Third-party
supplied
alongside
listed.
Cross-module
dependencies
described
general
level.
depend
Core.
Module/Tool
Component
Description
Notes
QSegfaultHandler
Parts
implementation
BSD-style
QUrl
Implementation
QUrl::fromUserInput().
Modified
BSD
Cocoa
Platform
Plugin
OS
X
port.
qtmain
library
A
helper
writing
cross-platform
main()
Windows.
Windows
Shift-JIS
Text
Codec
character
encoding
Japanese.
ISO--JP
(JIS)
widely
EUC-JP
variable-width
three
Japanese
standards.
EUC-KR
TextCodec
Extended
Unix
(EUC)
multibyte
system
primarily
Japanese,
Korean,
simplified
Chinese.
GBK
extension
GB2312
Chinese
characters,
mainland
China.
Big5
Big5,
BIG-,
method
Traditional
characters.
Big5-HKSCS
TSCII
codec
conversion
Tamil
encoding.
Stack-less
Just-In-Time
compiler
platform-independent
JIT
compiler.
codecs
Unicode
data.
Permissive,
GPL-compatible
Macros
building
files
CMake
Qt.
PCRE
regular
expression
pattern
matching
syntax
semantics
Perl
.
Android
Run-time
run-time
(libstdc++)
Android.
GPLv3
exception
forkfd
tool
facilitate
spawning
sub-processes.
MIT
systems
FreeBSD
strtoll
strtoull
Functions
converting
integer.
V8
strings
doubles.
MD4
implements
message-digest
algorithm.
MD5
Mesa
llvmpipe
rasterizer
backend
(opengl32sw.dll)
builds.
SHA-
encryption
SHA-
zlib
purpose
data
compression
library.
Suffix
List
list
known
Internet
suffixes.
Mozilla
Gui
QKeyMapper
Internal
key
mapping.
Custom,
Linux/X11
QImage
smooth
scaling
QImage::transformed().
FreeType
project
font
rendering.
GPLv2,
Project
HarfBuzz
OpenType
layout
engine.
PNG
Library
reducing
effort
takes
support
format.
Pixman
low-level
pixel
manipulation
features
such
image
compositing
trapezoid
rasterization.
Drag
Drop
Allows
users
transfer
within
applications.
ANGLE
Opensource
map
OpenGL
ES
API
calls
DirectX
API.
Location
Poly2Tri
sweepline
constrained
Delaunay
Polygon
Triangulation
Library.
FFTReal
Fast
Fourier
transform
real-valued
arrays.
(Used
example
code).
Canvas
3D
three.js
JavaScript
code)
Three.js
Loader
parser
loading
models
JSON
structures.
gl-matrix.js
High
performance
matrix
vector
SVG
arc
handling
module.
Depends
Gui,
Widgets
Quick
Easing
Equations
collection
swappable
add
flavor
motion.
QML,
Network
Controls
Native
Style
Apache
Script
(Provided
compatibility)
benchmark
tests
Script.
Sunspider
JavaScriptCore
v2
Testlib
BSD,
Valgrind
analysis
detecting
leaks.
valgrind.h
Callgrind
profiling
tool.
Print
Support
PDF
Licensing.
Wayland
Protocol
WebEngine
v3
+
Chromium
LGPLv2.,
BSL,
Apache,
APSL,
MIT,
MPL,
others
Designer
recursive
shadow
casting
algorithm
Designer.
(MIT)
Botan
crypto
Creator.
Image
Formats
JasPer
coding
images.
TIFF
libtiff
(a
library)
files.
MNG
decoding
displaying
format
WebP
SQL
SQLite
self-contained,
embeddable,
zero-configuration
database
XML
Patterns
Bison
Parser
generator.
assimp
Open
Asset
Import
Plugins
JPEG
decompression.
IAccessible2
An
accessibility
Microsoft
Cycle
CPU
tick
counter.
callgrind.h
xcb
language
binding
Window
System.
at-spi
at-spi2
toolkit-neutral
way
providing
facilities
application.
xkbcommon
Keymap
toolkits
window
systems.
Clucene
high-performance,
full-featured
text
search
engine
C++.
LGPL/Apache
licenses:
Charts
Visualization
Virtual
Keyboard
Lipi
Toolkit
open
toolkit
online
Handwriting
Recognition
(HWR).
MIT-Style
OpenWnn
IME
Pinyin
Standard
input.
tcime
traditional
IME.
2D
Renderer
EGL
Headers
These
headers
based
specification.
SGI
OpenKODE
Header
header
Qml
Macro
Assembler
assembly
generated
JIT.
documents
below
related
documents,
Trademark
Provides
additional
Contributions
Files
contributions
Apple,
Inc.
Fonts
Embedded
Linux
fonts
Details
restrictions
PDF-related
trademarks.
Source
Describes
Third-Party
third-party
Trademarks
trademarks
owned
Company
organizations.
Ltd.
included
herein
copyrights
respective
owners.
logos
Finland
and/or
countries
worldwide.
property
Start
Terms
&
Conditions
FAQ
Product
Use
Commercial
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Technology
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Forums
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Us
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QObject
Properties
Slots
Signals
Static
Members
Protected
Related
Non-Members
Detailed
Thread
Affinity
No
Copy
Constructor
Assignment
Operator
Auto-Connection
Internationalization
(I18n)
Class
objects.
More...
Header:
#include
<QObject>
qmake:
QT
+=
core
Instantiated
By:
QtObject
Inherited
Q3DObject,
Q3DScene,
Q3DTheme,
QAbstract3DAxis,
QAbstract3DInputHandler,
QAbstract3DSeries,
QAbstractAnimation,
QAbstractAxis,
QAbstractDataProxy,
QAbstractEventDispatcher,
QAbstractItemDelegate,
QAbstractItemModel,
QAbstractMessageHandler,
QAbstractNetworkCache,
QAbstractSeries,
QAbstractState,
QAbstractTextDocumentLayout,
QAbstractTransition,
QAbstractUriResolver,
QAbstractVideoFilter,
QAbstractVideoSurface,
QAccessiblePlugin,
QAction,
QActionGroup,
QAudioInput,
QAudioOutput,
QAudioProbe,
QAxFactory,
QAxObject,
QAxScript,
QAxScriptManager,
QBarSet,
QBluetoothDeviceDiscoveryAgent,
QBluetoothLocalDevice,
QBluetoothServer,
QBluetoothServiceDiscoveryAgent,
QBluetoothTransferManager,
QBluetoothTransferReply,
QBoxSet,
QButtonGroup,
QCameraExposure,
QCameraFocus,
QCameraImageCapture,
QCameraImageProcessing,
QCanBus,
QCanBusDevice,
QClipboard,
QCompleter,
QCoreApplication,
QCustom3DItem,
QDataWidgetMapper,
QDBusAbstractAdaptor,
QDBusAbstractInterface,
QDBusPendingCallWatcher,
QDBusServer,
QDBusServiceWatcher,
QDBusVirtualObject,
QDesignerFormEditorInterface,
QDesignerFormWindowManagerInterface,
QDnsLookup,
QDrag,
QEventLoop,
QExtensionFactory,
QExtensionManager,
QFileSelector,
QFileSystemWatcher,
QGamepad,
QGenericPlugin,
QGeoAreaMonitorSource,
QGeoCodeReply,
QGeoCodingManager,
QGeoCodingManagerEngine,
QGeoPositionInfoSource,
QGeoRouteReply,
QGeoRoutingManager,
QGeoRoutingManagerEngine,
QGeoSatelliteInfoSource,
QGeoServiceProvider,
QGesture,
QGLShader,
QGLShaderProgram,
QGraphicsAnchor,
QGraphicsEffect,
QGraphicsItemAnimation,
QGraphicsObject,
QGraphicsScene,
QGraphicsTransform,
QHelpEngineCore,
QHelpSearchEngine,
QHttpMultiPart,
QIconEnginePlugin,
QImageIOPlugin,
QInAppProduct,
QInAppStore,
QInAppTransaction,
QInputMethod,
QIODevice,
QItemSelectionModel,
QJSEngine,
QLayout,
QLegendMarker,
QLibrary,
QLocalServer,
QLowEnergyController,
QLowEnergyService,
QMacToolBar,
QMacToolBarItem,
QMaskGenerator,
QMediaControl,
QMediaObject,
QMediaPlaylist,
QMediaRecorder,
QMediaService,
QMediaServiceProviderPlugin,
QMimeData,
QModbusDevice,
QModbusReply,
QMovie,
QNearFieldManager,
QNearFieldShareManager,
QNearFieldShareTarget,
QNearFieldTarget,
QNetworkAccessManager,
QNetworkConfigurationManager,
QNetworkCookieJar,
QNetworkSession,
QObjectCleanupHandler,
QOffscreenSurface,
QOpenGLContext,
QOpenGLContextGroup,
QOpenGLDebugLogger,
QOpenGLShader,
QOpenGLShaderProgram,
QOpenGLTimeMonitor,
QOpenGLTimerQuery,
QOpenGLVertexArrayObject,
QPdfWriter,
QPictureFormatPlugin,
QPieSlice,
QPlaceManager,
QPlaceManagerEngine,
QPlaceReply,
QPlatformGraphicsBuffer,
QPlatformSystemTrayIcon,
QPluginLoader,
QQmlComponent,
QQmlContext,
QQmlExpression,
QQmlExtensionPlugin,
QQmlFileSelector,
QQmlNdefRecord,
QQmlPropertyMap,
QQuickImageResponse,
QQuickItem,
QQuickItemGrabResult,
QQuickRenderControl,
QQuickTextDocument,
QQuickTextureFactory,
QQuickWebEngineProfile,
QRadioData,
QScreen,
QScriptEngine,
QScriptEngineDebugger,
QScriptExtensionPlugin,
QScroller,
QScxmlDataModel,
QScxmlStateMachine,
QSensor,
QSensorBackend,
QSensorGesture,
QSensorGestureManager,
QSensorGestureRecognizer,
QSensorReading,
QSessionManager,
QSettings,
QSGAbstractRenderer,
QSGEngine,
QSGTexture,
QSGTextureProvider,
QSharedMemory,
QShortcut,
QSignalMapper,
QSignalSpy,
QSocketNotifier,
QSound,
QSoundEffect,
QSqlDriver,
QSqlDriverPlugin,
QStyle,
QStyleHints,
QStylePlugin,
QSvgRenderer,
QSyntaxHighlighter,
QSystemTrayIcon,
Qt3DCore::QAbstractAspect,
Qt3DCore::QAspectEngine,
Qt3DCore::QNode,
Qt3DCore::Quick::QQmlAspectEngine,
Qt3DInput::QKeyEvent,
Qt3DInput::QMouseEvent,
Qt3DInput::QWheelEvent,
Qt3DRender::QGraphicsApiFilter,
Qt3DRender::QPickEvent,
Qt3DRender::QTextureWrapMode,
QTcpServer,
QTextDocument,
QTextObject,
QThread,
QThreadPool,
QTimeLine,
QTimer,
QTranslator,
QtVirtualKeyboard::InputContext,
QtVirtualKeyboard::InputEngine,
QtVirtualKeyboard::ShiftHandler,
QUiLoader,
QUndoGroup,
QUndoStack,
QValidator,
QValue3DAxisFormatter,
QVideoProbe,
QWaylandClient,
QWaylandSurfaceGrabber,
QWaylandView,
QWebChannel,
QWebChannelAbstractTransport,
QWebEngineCookieStore,
QWebEngineDownloadItem,
QWebEnginePage,
QWebEngineProfile,
QWebEngineUrlRequestInterceptor,
QWebEngineUrlRequestJob,
QWebEngineUrlSchemeHandler,
QWebSocket,
QWebSocketServer,
QWidget,
QWindow,
QWinEventNotifier,
QWinJumpList,
QWinTaskbarButton,
QWinTaskbarProgress,
QWinThumbnailToolBar,
QWinThumbnailToolButton
members,
including
inherited
members
Obsolete
reentrant.
thread-safe:
connect(
*sender,
*signal,
*receiver,
*method,
Qt::ConnectionType
type)
PointerToMemberFunction
signal,
method,
Functor
functor)
*context,
functor,
disconnect(
*method)
method)
objectName
QString
QObject(QObject
*parent
Q_NULLPTR)
~QObject()
blockSignals(
block)
QObjectList
children()
QMetaObject::Connection
Qt::AutoConnection)
*signal
Q_NULLPTR,
*receiver
*method
dumpObjectInfo()
dumpObjectTree()
QList<QByteArray>
dynamicPropertyNames()
*e)
eventFilter(QObject
*watched,
QEvent
*
findChild(
&name
QString(),
Qt::FindChildOptions
Qt::FindChildrenRecursively)
QList<T>
findChildren(
QRegExp
®Exp,
QRegularExpression
&re,
inherits(
*className)
installEventFilter(QObject
*filterObj)
isWidgetType()
isWindowType()
killTimer(
id)
QMetaObject
*
metaObject()
moveToThread(QThread
*targetThread)
objectName()
parent()
QVariant
property(
*name)
removeEventFilter(QObject
*obj)
setObjectName(
&name)
setParent(QObject
*parent)
setProperty(
*name,
&value)
signalsBlocked()
startTimer(
interval,
Qt::TimerType
timerType
Qt::CoarseTimer)
QThread
thread()
deleteLater()
destroyed(QObject
*obj
objectNameChanged(
&objectName)
QMetaMethod
&signal,
&method,
&method)
&connection)
staticMetaObject
tr(
*sourceText,
*disambiguation
n
-)
childEvent(QChildEvent
connectNotify(
&signal)
customEvent(QEvent
disconnectNotify(
isSignalConnected(
receivers(
*signal)
sender()
senderSignalIndex()
timerEvent(QTimerEvent
typedef
qFindChildren(
*obj,
®Exp)
qobject_cast(QObject
*
Q_CLASSINFO(Name,
Value)
Q_DISABLE_COPY(Class)
Q_EMIT
Q_ENUM(...)
Q_FLAG(...)
Q_GADGET
Q_INTERFACES(...)
Q_INVOKABLE
Q_OBJECT
Q_PROPERTY(...)
Q_REVISION
Q_SET_OBJECT_NAME(Object)
Q_SIGNAL
Q_SIGNALS
Q_SLOT
Q_SLOTS
heart
Object
Model.
central
feature
powerful
mechanism
seamless
communication
called
signals
slots.
You
connect
signal
slot
connect()
destroy
connection
disconnect().
avoid
never
ending
notification
loops
temporarily
block
blockSignals().
connectNotify()
disconnectNotify()
make
possible
track
connections.
QObjects
organize
themselves
trees.
When
create
parent,
will
itself
parent's 1
list.
parent
ownership
i.e.,
children
destructor.
look
name
optionally
findChild()
findChildren().
Every
has
found
via
corresponding
(see
QMetaObject::className()).
determine
object's 13
inherits
inheritance
hierarchy
inherits()
function.
deleted,
emits
destroyed()
signal.
dangling
QObjects.
receive
events
filter
installEventFilter()
eventFilter()
convenience
handler,
childEvent(),
reimplemented
child
events.
Last
least,
basic
timer
Qt;
QTimer
high-level
timers.
Notice
macro
mandatory
signals,
slots
properties.
need
run
Meta
Compiler
file.
We
strongly
recommend
subclasses
regardless
actually
properties,
since
failure
so
lead
exhibit
strange
widgets
inherit
QObject.
returns
widget.
It
much
faster
qobject_cast<QWidget
*>(obj)
obj->inherits(
functions,
e.g.
children(),
QObjectList.
QList<QObject
*>.
instance
said
thread
affinity,
lives
thread.
receives
queued
posted
handler
If
no
affinity
(that
zero),
running
loop,
then
created.
queried
changed
moveToThread().
must
live
parent.
Consequently:
setParent()
fail
involved
threads.
moved
thread,
too.
moveToThread()
created
QThread::run(),
because
does
QThread::run().
QObject's 1
variables
children.
parent-child
relationship
either
passing
child's 2
constructor,
calling
setParent().
Without
step,
remain
old
when
called.
neither
copy
constructor
nor
assignment
This
design.
Actually,
declared,
section
Q_DISABLE_COPY().
In
fact,
classes
derived
(direct
indirect)
declare
reasoning
discussion
Identity
vs
Value
Model
page.
main
consequence
should
pointers
your
subclass)
might
tempted
subclass
value.
example,
without
can't 1
stored
one
classes.
pointers.
Qt's 11
meta-
As
objects
defined
suitable
names,
follow
simple
naming
convention,
performed
QMetaObject::connectSlotsByName()
uic
generates
invokes
enable
auto-connection
forms
More
given
Using
UI
File
Your
manual.
From
added
removed
instances
run-time.
declared
compile-time,
yet
advantages
manipulated
property()
read
setProperty()
write
them.
supported
Designer,
standard
user-created
translation
features,
making
translate
application's 1
user
into
languages.
user-visible
translatable,
wrapped
tr()
explained
detail
Writing
Translation
document.
QMetaObject,
QPointer,
Q_DISABLE_COPY(),
Trees
Ownership.
Property
holds
find
(and
findChild().
qDebug("MyClass::setPrecision(): 1
(%s)
invalid
precision
%f", 1
qPrintable(objectName()),
newPrecision);
contains
Notifier
signal:
[see
note
below]
connections
emitted
user.
QMetaObject::className().
Function
QObject::QObject(QObject
Constructs
viewed
owner.
instance,
dialog
box
OK
Cancel
buttons
contains.
destroys
Setting
constructs
widget,
top-level
window.
parent(),
findChild(),
[
QObject::~QObject()
Destroys
deleting
disconnected,
pending
However,
often
safer
rather
directly.
Warning:
deleted.
these
stack
sooner
later
program
crash.
holding
outside
still
gives
opportunity
detect
destroyed.
Deleting
waiting
delivered
cause
exists
currently
executing.
instead,
loop
after
been
it.
deleteLater().
QObject::blockSignals(
blocked
(i.e.,
emitting
invoke
anything
connected
it).
blocking
occur.
previous
signalsBlocked().
Note
even
blocked.
being
buffered.
QSignalBlocker.
[
QObject::childEvent(QChildEvent
passed
parameter.
QEvent::ChildAdded
QEvent::ChildRemoved
sent
removed.
cases
rely
QObject,
QWidget.
(This
because,
ChildAdded
fully
constructed,
ChildRemoved
destructed
already).
QEvent::ChildPolished
polished,
polished
added.
construction
completed.
guaranteed,
multiple
polish
during
execution
widget's 1
constructor.
every
zero
ChildPolished
events,
omitted
immediately
several
times
destruction,
child,
each
table.
&QObject::children()
Returns
file
following:
QList<QObject*>
QObjectList;
list,
i.e.
appended
order
changes
QWidget
raised
lowered.
widget
becomes
lowered
findChildren(),
[
QObject::connect(
Creates
sender
receiver
disconnect
later.
SIGNAL()
SLOT()
macros
specifying
example:
QLabel
*label
QLabel;
QScrollBar
*scrollBar
QScrollBar;
QObject::connect(scrollBar,
SIGNAL(valueChanged(
label,
SLOT(setNum(
ensures
label
always
displays
current
scroll
bar
contain
variable
type.
E.g.
would
// 26
WRONG
SIGNAL(valueChanged(
value)),
SLOT(setNum(
value)));
MyWidget
{
MyWidget();
signals:
buttonClicked();
QPushButton
*myButton;
};
MyWidget::MyWidget()
myButton
QPushButton(
connect(myButton,
SIGNAL(clicked()),
SIGNAL(buttonClicked()));
}
relays
variable,
makes
relates
MyWidget.
many
signals.
Many
slot.
slots,
activated
were
made,
emitted.
represents
successfully
connects
connection,
unable
verify
existence
signatures
aren't 1
compatible.
check
valid
make;
duplicate
disconnect()
call.
pass
Qt::UniqueConnection
made
duplicate.
there
already
(exact
exact
objects),
QMetaObject::Connection.
optional
describes
establish.
particular,
determines
particular
delivery
time.
queued,
system,
arguments
behind
scenes.
error
message
QObject::connect:
Cannot
(Make
sure
registered
qRegisterMetaType().)
call
qRegisterMetaType()
register
before
establish
connection.
thread-safe
disconnect(),
sender(),
qRegisterMetaType(),
Q_DECLARE_METATYPE().
Connection
invalid.
works
specify
method.
was
introduced
type).
connect().
Connects
Equivalent
connect(sender,
emit
header.
least
slot,
Example:
QLineEdit
*lineEdit
QLineEdit;
QObject::connect(lineEdit,
&QLineEdit::textChanged,
&QLabel::setText);
line
edit
text.
(
signal)
argument
Q_DECLARE_METATYPE
Overloaded
resolved
help
qOverload.
number
limited
C++
variadic
templates.
functor
exactly
arguments.
There
exist
someFunction();
*button
QPushButton;
QObject::connect(button,
&QPushButton::clicked,
someFunction);
lambda
expressions,
them:
QByteArray
...;
QTcpSocket
*socket
QTcpSocket;
socket->connectToHost(
);
QObject::connect(socket,
&QTcpSocket::connected,
[=]
()
socket->write("GET 2
" 2
"
});
take
care
alive
templates,
,
overloaded
templated
placed
context,
someFunction,
Qt::QueuedConnection);
},
Qt::AutoConnection);
context
QObject::connectNotify(
something
compare
QMetaMethod::fromSignal()
follows:
(signal
==
QMetaMethod::fromSignal(&MyObject::valueChanged))
valueChanged
violates
principle
modularity.
useful
expensive
initialization
performs
lives.
disconnectNotify().
QObject::customEvent(QEvent
custom
Custom
user-defined
large
QEvent::User
item
QEvent::Type
typically
subclass.
QEvent.
[slot]
QObject::deleteLater()
Schedules
deletion.
deleted
control
loop.
(e.g.
QCoreApplication::exec()),
once
started.
stopped,
Since
destroyed
finishes.
entering
leaving
(e.g.,
opening
modal
dialog)
deferred
deletion;
safe
once;
delivered,
QPointer.
[signal]
QObject::destroyed(QObject
obj
destroyed,
objects's 1
QObject::disconnect(
Disconnects
receiver.
broken;
signal-slot
examples
demonstrate.
Disconnect
everything
disconnect(myObject,
,
);
equivalent
non-
myObject->disconnect();
SIGNAL(mySignal()),
myObject->disconnect(SIGNAL(mySignal()));
receiver:
myReceiver,
myObject->disconnect(myReceiver);
wildcard,
meaning
"any 9
signal", 2
receiving
object", 4
respectively.
.
(You
call.)
disconnects
not,
specified
disconnected.
named
left
alone.
specifically-named
possibilities
Additionally
returnsfalse
disconnected
QMetaMethod()
wildcard
signal" 1
object". 2
QMetaMethod().
*method).
receiver's 1
nothing
diconnect().
&MyObject::mySignal(),
slot:
QObject::disconnect(lineEdit,
overload
diconnect
functors
expressions.
That
Instead,
QObject::disconnectNotify(
how
),
once,
(QMetaMethod::isValid()
optimizing
resources.
disconnection,
mutex
locked.
therefore
allowed
re-enter
reimplementation
reimplementation,
don't 2
held
places
result
deadlock.
connectNotify().
QObject::dumpObjectInfo()
Dumps
connections,
etc.
debug
output.
debugging,
compiled
release
mode
(i.e.
debugging
information).
dumpObjectTree().
QObject::dumpObjectTree()
tree
dumpObjectInfo().
QObject::dynamicPropertyNames()
names
setProperty().
QObject::
e
recognized
processed.
customize
behavior
Make
did
handle.
MyClass
MyClass(QWidget
~MyClass();
ev)
(ev->type()
QEvent::PolishRequest)
overwrite
PolishRequest
doThings();
QEvent::Show)
complement
Show
doThings2();
QWidget::
rest
installEventFilter(),
timerEvent(),
QCoreApplication::sendEvent(),
QCoreApplication::postEvent().
QObject::eventFilter(QObject
Filters
installed
watched
function,
stop
further,
MainWindow
QMainWindow
MainWindow();
*ev);
QTextEdit
*textEdit;
MainWindow::MainWindow()
textEdit
QTextEdit;
setCentralWidget(textEdit);
textEdit->installEventFilter(
MainWindow::eventFilter(QObject
(obj
textEdit)
(
QEvent::KeyPress)
QKeyEvent
*keyEvent
static_cast<QKeyEvent*>(
qDebug()
<<
"Ate 1
press" 1
keyEvent->key();
QMainWindow::eventFilter(obj,
above
unhandled
class's 1
own
purposes.
Otherwise,
installEventFilter().
QObject::findChild(
cast
name,
Omitting
matched.
recursively,
unless
specifies
option
FindDirectChildrenOnly.
search,
most
ancestor
returned.
ancestors,
findChildren()
used.
parentWidget
button
isn't 2
parent:
parentWidget->findChild<QPushButton
*>(
QListWidget
parentWidget:
*list
parentWidget->findChild<QListWidget
*>();
(its
parent)
*>(
Qt::FindDirectChildrenOnly);
parentWidget,
*>(QString(),
QObject::findChildren(
shows
QWidgets
widgetname:
QList<QWidget
*>
parentWidget.findChildren<QWidget
*>(
QPushButtons
QList<QPushButton
allPButtons
parentWidget.findChildren<QPushButton
immediate
childButtons
regExp,
re,
QObject::inherits(
className
className;
considered
itself.
*timer
QTimer;
timer->inherits(
timer->inherits(
timer->inherits(
QVBoxLayout
QLayoutItem
*layout
QVBoxLayout;
layout->inherits(
layout->inherits(
(even
though
QObject)
it,
consider
qobject_cast<Type
*>(
qobject_cast().
QObject::installEventFilter(QObject
Installs
filterObj
monitoredObj->installEventFilter(filterObj);
filtered,
stopped);
filters
first.
Here's 1
KeyPressEater
eats
presses
monitored
objects:
...
*
KeyPressEater::eventFilter(QObject
static_cast<QKeyEvent
*>(
qDebug("Ate 1
press
%d", 1
keyEvent->key());
processing
QObject::eventFilter(obj,
And
here's 1
install
widgets:
*keyPressEater
KeyPressEater(
*pushButton
QListView
*listView
QListView(
pushButton->installEventFilter(keyPressEater);
listView->installEventFilter(keyPressEater);
QShortcut
technique
intercept
shortcut
presses.
sends
filtering
nothing.
until
again
(it
removed).
removeEventFilter(),
eventFilter(),
[
QObject::isSignalConnected(
receiver,
behaviour
undefined.
valueChangedSignal
QMetaMethod::fromSignal(&MyObject::valueChanged);
(isSignalConnected(valueChangedSignal))
data;
get_the_value();
operation
valueChanged(data);
snippet
illustrates,
nobody
listens
to.
QObject::isWidgetType()
widget;
Calling
inherits(
except
faster.
QObject::isWindowType()
window;
inherits(
QObject::killTimer(
Kills
identifier,
id.
identifier
returned
startTimer()
timerEvent()
startTimer().
*QObject::metaObject()
superclass
meta-
required
signal/slot
system.
actual
staticMetaObject.
obj->metaObject()->className();
QPushButton::staticMetaObject.className();
QObject::moveToThread(QThread
Changes
Event
targetThread.
move
QApplication::instance()
retrieve
application,
QApplication::thread()
application
myObject->moveToThread(QApplication::instance()->thread());
targetThread
zero,
stops.
active
timers
reset.
stopped
restarted
(with
interval)
result,
constantly
moving
threads
postpone
indefinitely.
QEvent::ThreadChange
just
changed.
special
processing.
thread-safe;
affinity.
words,
arbitrary
thread().
QObject::objectNameChanged(
objectName.
QObject::objectName.
*QObject::parent()
children().
QObject::property(
property.
exists,
variant
dynamicPropertyNames().
setProperty(),
QVariant::isValid(),
metaObject(),
QObject::receivers(
receivers
times,
(receivers(SIGNAL(valueChanged(QByteArray)))
)
get_the_value(&data);
isSignalConnected().
QObject::removeEventFilter(QObject
Removes
request
ignored
installed.
remove
filter,
activation
function).
*QObject::sender()
signal;
context.
sender's 1
getting
mentioned
above,
Qt::DirectConnection
Do
scenario.
QSignalMapper.
QObject::senderSignalIndex()
meta-method
index
executing
sender().
-
parameters,
indexes
parameter),
apply
overloading
parameters.
QMetaObject::indexOfSignal(),
QMetaObject::method().
QObject::setParent(QObject
Makes
QObject::setProperty(
Sets
Q_PROPERTY
success
otherwise.
Q_PROPERTY,
listed
meta-
setting
QVariant.
Changing
QDynamicPropertyChangeEvent
starting
property(),
dynamicPropertyNames(),
QMetaProperty::write().
QObject::signalsBlocked()
blocked;
blockSignals()
QObject::startTimer(
Starts
could
start
timer.
occur
interval
milliseconds
killTimer()
occurs
process.
QTimerEvent
occurs.
Reimplement
running,
QTimerEvent::timerId()
activated.
MyObject
MyObject(QObject
MyObject::MyObject(QObject
QObject(parent)
startTimer();
-millisecond
startTimer();
-second
startTimer();
-minute
MyObject::timerEvent(QTimerEvent
"Timer 1
ID:" 1
QTimer's 1
accuracy
depends
underlying
operating
hardware.
types.
Most
platforms
milliseconds;
more.
deliver
requested
silently
discard
some.
programming
single-shot
instead
QBasicTimer
lightweight
clumsy
IDs
killTimer(),
QTimer::singleShot().
*QObject::thread()
QObject::timerEvent(QTimerEvent
higher-level
functionality,
startTimer(),
QObject::tr(
translated
sourceText,
disambiguation
containing
plurals;
QString::fromUtf8(sourceText)
available.
MainWindow::createActions()
QMenu
*fileMenu
menuBar()->addMenu(tr(
sourceText
roles
identifying
(
earlier,
preferred
comments
translators.
MyWindow::MyWindow()
*senderLabel
QLabel(tr(
*recipientLabel
QLabel(tr(
detailed
description
mechanisms
general,
Disambiguation
disambiguation.
reentrant
translators
Installing
removing
performing
translations
supported.
Doing
probably
crashes
undesirable
QCoreApplication::translate()
Variable
QObject::staticMetaObject
stores
associated
metaObject().
Synonym
qFindChildren().
obj->findChildren<T>(regExp).
workaround
MSVC
functions.
advised
code.
QObject::findChildren().
subclass);
(directly
indirectly)
macro.
qobject_cast<QTimer
*>(obj);
(QObject
*)obj
QAbstractButton
qobject_cast<QAbstractButton
qobject_cast()
behaves
similarly
dynamic_cast(),
doesn't 4
require
RTTI
across
boundaries.
conjunction
interfaces;
Plug
Paint
macro,
function's 1
QObject::inherits().
associates
extra
QObject::metaObject().
feature,
Active
Qt,
D-Bus
QML.
Name
literal
Q_CLASSINFO(
"Pierre 1
Gendron") 1
Q_CLASSINFO(
QMetaObject::classInfo(),
Adaptors,
Extending
Disables
constructors
Class.
Instances
thought
values
copied
assigned,
unique
identities.
means
(director
indirect),
give
enough
simply
omit
mistakenly
requires
(it's 1
easy
thoughtfully
you.
curious
seen
include
section:
Q_DISABLE_COPY(MyClass)
declares
section,
mistake,
report
error.
MyClass(
&);
&
absolutely
w
QWidget();
First
all,
that.
compilers
generate
privacy
violation
reported,
statement
way.
we
crash
w.
replace
keyword
3rd
party
mechanism.
normally
no_keywords
CONFIG
.pro
file,
specified.
registers
declaration
MyClass(QObject
Priority
High,
Low,
VeryHigh,
VeryLow
Q_ENUM(Priority)
setPriority(Priority
priority);
priority()
Enumerations
Q_ENUM
QMetaEnum
enclosing
QMetaObject.
QMetaEnum::fromType()
QMetaEnum.
Registered
enumerations
meta
QMetaType
features;
QVariant,
convert
strings.
Likewise,
QDebug
print
names.
flags
combined
bitwise
OR
declaration.
LoadHints
flag
way:
QLibrary
LoadHint
ResolveAllSymbolsHint
ExportExternalSymbolsHint
LoadArchiveMemberHint
Q_DECLARE_FLAGS(LoadHints,
LoadHint)
Q_FLAG(LoadHints)
itself,
Q_DECLARE_FLAGS()
Q_FLAG
registering
unnecessary
Q_ENUM()
addition
lighter
reflection
capabilities
offered
Just
appear
definition.
Q_GADGETs
Q_ENUM,
Q_INVOKABLE,
member,
staticMetaObject,
enums
Q_ENUMS.
tells
interfaces
implements.
implementing
plugins.
BasicToolsPlugin
BrushInterface,
ShapeInterface,
FilterInterface
Q_PLUGIN_METADATA(IID
FILE
Q_INTERFACES(BrushInterface
ShapeInterface
FilterInterface)
Basic
Q_DECLARE_INTERFACE(),
Q_PLUGIN_METADATA(),
How
Create
Plugins.
Apply
declarations
invoked
shown
Window();
normalMethod();
invokableMethod();
invokableMethod()
marked
up
causing
enabling
QMetaObject::invokeMethod().
normalMethod()
way,
services
Counter
Counter()
m_value
;
value()
m_value;
slots:
setValue(
value);
valueChanged(
newValue);
system's 1
Meta-Object
System,
Slots,
declaring
behave
accessible
Q_PROPERTY(type
(READ
getFunction
[WRITE
setFunction]
MEMBER
memberName
[(READ
WRITE
setFunction)])
[RESET
resetFunction]
[NOTIFY
notifySignal]
[REVISION
[DESIGNABLE
[SCRIPTABLE
[STORED
[USER
[CONSTANT]
[FINAL])
READ
required.
items
optional,
common.
attributes
USER,
Q_PROPERTY(QString
title
setTitle
USER
details
use,
tag
revision
Q_PROPERTY(
normalProperty
normalProperty)
newProperty
REVISION
)
normalProperty();
newProperty();
Q_REVISION()
newMethod();
expose
API,
match
expected
versions
Consider
expectedRevision
*windowMetaObject
window.metaObject();
(
i=;
i
windowMetaObject->methodCount();
i++)
(windowMetaObject->method(i).revision()
<=
expectedRevision)
exposeMethod(windowMetaObject->method(i));
windowMetaObject->propertyCount();
(windowMetaObject->property(i).revision()
exposeProperty(windowMetaObject->property(i));
newMethod
exposed
greater.
methods
untagged,
Q_REVISION()
ignored.
Currently
QtQml
generic
tag,
QMetaMethod::tag()
QMetaMethod::revision().
assigns
matter
figures
QObject::objectName().
mark
useful,
3rd-party
understand
groups.
declarations,
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