ios 协议（delegate）使用过程中遇到assign attribute must be unsafeunretained

今天在使用协议的过程中，偶然发现这样使用

 

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@interfaceAppDelegate (){

    id<chatdelegate>  testdelegate;

}

@property(nonatomic , assign) id<chatdelegate> testdelegate;

 

@end

 

@implementationAppDelegate

@synthesizetestdelegate;

</chatdelegate></chatdelegate>

会报错：

 

Existing instance variable 'delegate' for property 'delegate' with assign attribute must be unsafe unretained

修改成：

 

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@interfaceAppDelegate (){

   __unsafe_unretained id<chatdelegate>  testdelegate;

}

@property(nonatomic , assign) id<chatdelegate> testdelegate;

 

@end

 

@implementationAppDelegate

@synthesizetestdelegate;

</chatdelegate></chatdelegate>

就好了，这只是为了相容iOS4以下的版本