创建一个买票协议.该协议规定输出是否还有剩票

1 #import 
      
       2 3 @protocol BuyticketsDelegate 
       
        4 5 @required6 - (void) check;7 8 @end
       
      

创建一个代理Agent遵守协议

1 #import "Buytickets.h" 2 @interface Agents : NSObject
      
        3  4 @end 5  6  7 @implementation Agents 8  9 - (void)check{10     NSLog(@"还有剩票");11 }12 13 @end
      

创建一个Person类，包含一个遵守协议的代理对象

1 @interface Person : NSObject 2  3 @property(nonatomic, assign)id
      
       delegate; 4  5 - (void)buy; 6  7 @end 8  9 10 #import "Person.h"11 @implementation Person12 13 - (void)buy{14     [_delegate check];15 }16 17 @end
      

在main函数里，指定一个代理

1 int main(int argc, const char * argv[]) { 2    @autoreleasepool { 3         4        Person *person = [[Person alloc]init]; 5        Agents *age = [[Agents alloc]init]; 6        person.delegate = age; 7        [person buy]; 8  9         10     }11     return 0;12 }