Obj-C：类符合协议作为参数 [英] Obj-C: Class conform to protocol as parameter

问题描述

在目标c中，可以将类作为参数传递给方法：

   - （void）methodThatTakesClass :(类）theClass; 
  

并且可以传递符合协议的实例作为参数：

   - （void）myConformInstance：（id< MyProtocol>）theObject; 
  

是否可以使用组合功能。

解决方案

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是的。下面是一个有效的程序，它将记录NSObject类。

  #import< Foundation / Foundation.h> 
 void f（Class< NSObject> c）{
 NSLog（@％@，c）; 
} 
 int main（）{
 f（[NSObject class]）; 
} 
  

这将导致编译器错误，如果你试图传递一个类， t符合NSObject，如 Object 类。您还可以将其用于方法。

   - （void）printClass：（Class< NSObject>）c; 
  

In objective c it is possible to pass a class as parameter to a method:

- (void) methodThatTakesClass:(Class)theClass;

And it is possible to pass an instance that is conform to an protocol as parameter:

- (void) myConformInstance:(id <MyProtocol>)theObject;

Is it possible to use the combined functionality. A method which takes a class which is conform to a certain protocol.

Thanks.

解决方案

Yes. The following is a valid program which will log the NSObject class.

#import <Foundation/Foundation.h>
void f(Class <NSObject> c) {
    NSLog(@"%@",c);
}
int main() {
    f([NSObject class]);
}

This would cause a compiler error if you tried to pass a class which doesn't conform to NSObject, such as the Object class. You can also use it for methods.

- (void)printClass:(Class <NSObject>)c;

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