Qt多重继承时的信号与槽

时间：2022-08-07 18:13:15

最近在公司项目中开发串口，因为历史原因串口要包装一下，且包装类需要继承自一个纯C++类。

QSerialPort可以使用slot function来获取从串口读到的数据，以及写入串口的bytes个数。因此就给自己的类加了对应的槽函数。代码示例如下：

#include <QObject>

class CBase

{

public:

  CBase();

  ~CBase();

};

class CDerive:public CBase,public QObject

{

  Q_OBJECT

public:

  CDerive();

  ~CDerive();

public slots:

   void slot1();

  signals:

};

当然了，这段代码压根不能编译，错误如下:

debug/moc_CObejctTest.cpp:77:8: error: 'staticMetaObject' is not a member of 'CBase'

{ &CBase::staticMetaObject, qt_meta_stringdata_CDerive.data,

^

debug/moc_CObejctTest.cpp: In member function 'virtual void* CDerive::qt_metacast(const char)':

debug/moc_CObejctTest.cpp:94:12: error: 'qt_metacast' is not a member of 'CBase'

return CBase::qt_metacast(_clname);

^

debug/moc_CObejctTest.cpp: In member function 'virtual int CDerive::qt_metacall(QMetaObject::Call, int, void**)':

debug/moc_CObejctTest.cpp:99:11: error: 'qt_metacall' is not a member of 'CBase'

_id = CBase::qt_metacall(_c, _id, _a);

^

debug/moc_CObejctTest.cpp: In member function 'virtual void CDerive::qt_metacast(const char*)':

debug/moc_CObejctTest.cpp:95:1: warning: control reaches end of non-void function [-Wreturn-type]

}

^

Makefile.Debug:316: recipe for target 'debug/moc_CObejctTest.o' failed

mingw32-make[1]: *** [debug/moc_CObejctTest.o] Error 1

去查看Qt生成的moc文件:

const QMetaObject CDerive::staticMetaObject =

{

  {

    &CBase::staticMetaObject, //-----------------

    qt_meta_stringdata_CDerive.data,

    qt_meta_data_CDerive,

    qt_static_metacall,

    Q_NULLPTR,

  Q_NULLPTR

  }

};

注意其中有注释的一行，CBase并不是继承自QObject，所以也就不存在staticMetaObject类。 可是CDerive明明也有继承自QObject类，为啥生成的moc认到了CBase了呢

然后想到把QObject放到第一个父类的位置。如下:

class CDerive:public QObject,public CBase

这样就可以编译通过了。生成的moc如下:

const QMetaObject CDerive::staticMetaObject = {

 { &QObject::staticMetaObject, qt_meta_stringdata_CDerive.data,

 qt_meta_data_CDerive, qt_static_metacall, Q_NULLPTR, Q_NULLPTR}

};

这就尴尬了。 难道moc只认继承列表中第一个位置的？

这个问题有空要查一下。。。。O(∩_∩)O哈哈哈~

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