What is the difference between methods that are declared with - and methods that are declared with +
用-声明的方法和用+声明的方法之间有什么区别
e.g
如
- (void)methodname
+ (void)methodname
5 个解决方案
#1
42
Methods prefixed with - are instance methods. This means they can only be invoked on an instance of a class, eg:
以-为前缀的方法是实例方法。这意味着它们只能在类的实例上调用，例如:
[myStringInstance length];
Methods prefixed with + are class methods. This means they can be called on Classes, without needing an instance, eg:
以+开头的方法是类方法。这意味着可以在类上调用它们，而不需要实例，例如:
[NSString stringWithString:@"Hello World"];
#2
2
minus are instance methods (only accessible via an instantiated object)
负的是实例方法(仅可通过实例化对象访问)
plus are class methods (like in Java Math.abs(), you can use it without an instantited object)
另外还有类方法(如在Java Math.abs()中，您可以使用它而无需实例化对象)
#3
1
According to this page:
根据这个页面:
Instance methods begin with - and class level methods begin with +
实例方法以-和类级别方法以+开始。
See this SO question for more information.
更多信息请参见这个问题。
#4
0
The first is an instance method and the second is a class method. You should read Apple's Objective-C documentation to learn about the difference.
第一个是实例方法，第二个是类方法。您应该阅读苹果的Objective-C文档以了解其中的差异。
#5
0
+(void)methodname is a class variable and -(void)methodname is object variable.
+(void)methodname是类变量，-(void)methodname是对象变量。
Lets say you make a utility class that has a method to reverse string. The class you call MYUtility.
假设您创建了一个实用程序类，该类具有反转字符串的方法。称为MYUtility的类。
If you use +, like
如果你用+，比如
+ (NSString *)reverse:(NSString *)stringToReverse
You could use it directly like
你可以直接使用
NSString *reversed = [MYUtility stringToReverse:@"I Love objective C"];
if you used a -, like
如果你使用-，比如。
- (NSString *)reverse:(NSString *)stringToReverse
You have to use :
你必须使用:
MYUtility *myUtil = [[MYUtility alloc] init];
NSString *reversed = [myUtil stringToReverse:@"There are many ways to do the same thing"];
With the class based function, you just call directly, but you don't have access to any local variables besides #defines that you can do because the class isn't instantiated.
使用基于类的函数，您只需直接调用，但是除了#定义之外，您不能访问任何本地变量，因为类没有实例化。
But with the - (NSString you must instantiate the class before use, and you have access to all local variables.
但是对于- (NSString，在使用之前必须实例化类，并且可以访问所有的本地变量。
This isn't a pick one thing and stay with it, many classes have both, just look at the header file for NSString, it is littered with + functions and - functions.
这并不是一件简单的事情，很多类都有，看看NSString的头文件，它到处都是+函数和-函数。
#1
42
Methods prefixed with - are instance methods. This means they can only be invoked on an instance of a class, eg:
以-为前缀的方法是实例方法。这意味着它们只能在类的实例上调用，例如:
[myStringInstance length];
Methods prefixed with + are class methods. This means they can be called on Classes, without needing an instance, eg:
以+开头的方法是类方法。这意味着可以在类上调用它们，而不需要实例，例如:
[NSString stringWithString:@"Hello World"];
#2
2
minus are instance methods (only accessible via an instantiated object)
负的是实例方法(仅可通过实例化对象访问)
plus are class methods (like in Java Math.abs(), you can use it without an instantited object)
另外还有类方法(如在Java Math.abs()中，您可以使用它而无需实例化对象)
#3
1
According to this page:
根据这个页面:
Instance methods begin with - and class level methods begin with +
实例方法以-和类级别方法以+开始。
See this SO question for more information.
更多信息请参见这个问题。
#4
0
The first is an instance method and the second is a class method. You should read Apple's Objective-C documentation to learn about the difference.
第一个是实例方法，第二个是类方法。您应该阅读苹果的Objective-C文档以了解其中的差异。
#5
0
+(void)methodname is a class variable and -(void)methodname is object variable.
+(void)methodname是类变量，-(void)methodname是对象变量。
Lets say you make a utility class that has a method to reverse string. The class you call MYUtility.
假设您创建了一个实用程序类，该类具有反转字符串的方法。称为MYUtility的类。
If you use +, like
如果你用+，比如
+ (NSString *)reverse:(NSString *)stringToReverse
You could use it directly like
你可以直接使用
NSString *reversed = [MYUtility stringToReverse:@"I Love objective C"];
if you used a -, like
如果你使用-，比如。
- (NSString *)reverse:(NSString *)stringToReverse
You have to use :
你必须使用:
MYUtility *myUtil = [[MYUtility alloc] init];
NSString *reversed = [myUtil stringToReverse:@"There are many ways to do the same thing"];
With the class based function, you just call directly, but you don't have access to any local variables besides #defines that you can do because the class isn't instantiated.
使用基于类的函数，您只需直接调用，但是除了#定义之外，您不能访问任何本地变量，因为类没有实例化。
But with the - (NSString you must instantiate the class before use, and you have access to all local variables.
但是对于- (NSString，在使用之前必须实例化类，并且可以访问所有的本地变量。
This isn't a pick one thing and stay with it, many classes have both, just look at the header file for NSString, it is littered with + functions and - functions.
这并不是一件简单的事情，很多类都有，看看NSString的头文件，它到处都是+函数和-函数。