协议

main.m

#import <Foundation/Foundation.h>
#import "Girl.h"
#import "Boy.h"
int main(int argc, const char * argv[]) {
   
    Girl *zongru = [Girl girlWithName:@"zongru" gender:@"f"];
    Boy  *lol = [Boy boyWithName:@"luoluo" gender:@"m"];
    // 调用女孩类的_delegated的setter方法，将lol设置为女孩的代理
    [zongru setDelegated:lol];
    // 女孩饿了。
    [zongru hungry];
    [zongru poor];
    return 0;
}

Boy.h

#import <Foundation/Foundation.h>
#import "Girl.h"
// 我们在父类后使用尖括号+协议名的方式表示：该类遵守某协议
@interface Boy : NSObject  <YueFa>
{
    NSString *_name;
    NSString *_gender;
}

// 挣钱
- (void)makeMoney;
// 做饭
- (void)cook;

// 洗衣服
- (void)washing;
- (NSString *)name;
+ (instancetype)boyWithName:(NSString *)name gender:(NSString *)gender;
@end

Boy.m

#import "Boy.h"

@implementation Boy
- (instancetype)initWithName:(NSString *)name gender:(NSString *)gender{
    if ([super init]) {
        _name = name;
        _gender = gender;
    }
    return self;
}


//  男孩实现女孩协议中的方法
// 挣钱
- (void)makeMoney{
    NSLog(@"%@，我挣了500亿秘鲁币",_name);
}
// 做饭
- (void)cook{
    NSLog(@"%@，快来吃饭！",_name);
}

// 洗衣服
- (void)washing{
    NSLog(@"%@，我帮你洗白白",_name);
}

- (NSString *)name{
    return _name;
}
+ (instancetype)boyWithName:(NSString *)name gender:(NSString *)gender{
    return [[Boy alloc] initWithName:name gender:gender];
}
@end

Girl.h

#import <Foundation/Foundation.h>
@protocol YueFa <NSObject>

@required   //  使用@required修饰的方法是必须实现的方法，也是默认的状态
// 挣钱
- (void)makeMoney;
// 做饭
- (void)cook;
@optional   //  使用@optional修饰的方法，可以选择性的实现
// 洗衣服
- (void)washing;

@end
@interface Girl : NSObject
{
    NSString *_name;
    NSString *_gender;
    //  声明一个代理实例变量
    id <YueFa>_delegated;
    
    
}

// 给代理实例变量添加一个setter方法，就将那个宗儒的代理商：lol设置进实例变量中
- (void)setDelegated:(id <YueFa>)delegated;
- (NSString *)name;
+ (instancetype)girlWithName:(NSString *)name gender:(NSString *)gender;
// 宗儒饿了
- (void)hungry;
// 宗儒穷了
- (void)poor;
@end

Girl.m

#import "Girl.h"

@implementation Girl
-(instancetype)initWithName:(NSString *)name gender:(NSString *)gender{
    if (self =[super init]) {
        _gender = gender;
        _name = name;
    }
    return self;
}
- (NSString *)name{
    return _name;
}
+ (instancetype)girlWithName:(NSString *)name gender:(NSString *)gender{
    return [[Girl alloc]initWithName:name gender:gender];
}
// 实现_delegated的setter方法
- (void)setDelegated:(id<YueFa>)delegated{
    _delegated = delegated;
}
// 宗儒饿了
- (void)hungry{
    NSLog(@"我饿了！");
    // 女孩饿了，有代理去做饭
    [_delegated cook];
}

// 宗儒穷了
- (void)poor{
    NSLog(@"我穷了");
    [_delegated makeMoney];
}

@end