1 // ManDeleagte接口声明
 2 @protocol ManDeleagte <NSObject>
 3 -(void)onAgeChanged:(int)age;
 4 @end
 5 
 6 // ManListener实现
 7 @interface ManListener : NSObject<ManDeleagte>
 8 -(void)onAgeChanged:(int)age;
 9 @end
10 
11 // ManListener实现
12 @implementation ManListener
13 
14 -(void)onAgeChanged:(int)age{
15     NSLog(@"Age changed,Current age is %d",age);
16 }
17 @end

 1 // 协议 相当于C++语言中的接口
 2 @protocol IPeople <NSObject>
 3 -(int)getAge;
 4 -(NSString*)getName;
 5 -(void)setAge:(int)age;
 6 @end
 7 
 8 // 类定义  并实现IPeople接口  多个接口用,相隔
 9 @interface Man : NSObject<IPeople>{
10     int _age;
11 }
12 -(id)init;
13 -(int)getAge;
14 -(NSString*)getName;
15 -(void)setAge:(int)age;
16 
17 @property id<ManDeleagte> delegate;
18 
19 @end
20 
21 // 类实现
22 @implementation Man
23 -(int)getAge{
24     return _age;
25 }
26 
27 -(instancetype)init{
28     self = [super init];
29     if (self) {
30         self.delegate = nil;
31         _age = 20;
32     }
33     return self;
34 }
35 
36 -(NSString*)getName{
37     return @"jinpangpang";
38 }
39 
40 -(void)setAge:(int)age{
41     // 通知给外界
42     if (age!=_age) {
43         if (self.delegate) {
44             [self.delegate onAgeChanged:age];
45         }
46     }
47     _age = age;
48 }
49 @end

 1 // 调用
 2 int main(int argc, char * argv[]) {
 3     Man *m  = [[Man alloc] init];
 4     // 给对象指定一个delegate
 5     [m setDelegate:[[ManListener alloc]init]];
 6     [m setAge:21];
 7     
 8     NSLog(@"%@",[m getName]);
 9     NSLog(@"%d",[m getAge]);
10     @autoreleasepool {
11         return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
12     }
13 }

// 运行结果
2015-11-28 17:33:23.825 L15Protcal[8740:991452] Age changed,Current age is 21
2015-11-28 17:33:23.826 L15Protcal[8740:991452] jinpangpang
2015-11-28 17:33:23.827 L15Protcal[8740:991452] 21