OC-协议实现多继承

#import "ViewController.h"
#import "Programmer.h"
#import "Student.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    Programmer * grammer = [Programmer new];
    [grammer program];
    [grammer draw];
    [grammer sing];
    
    Student * student = [Student new];
    [student draw];
    [student sing];
}

#import <Foundation/Foundation.h>

// 编程技能
@protocol Program <NSObject>
- (void)program;
@end
// 绘画技能
@protocol Draw <NSObject>
- (void)draw;
@end
// 歌唱技能
@protocol Sing <NSObject>
- (void)sing;
@end

// 原本一个什么也不会的程序员
// 学会了多个技能
@interface Programmer : NSObject <Program, Draw, Sing>
// 继承的协议方法自动公有，无须声明接口
@end

#import "Programmer.h"

// 需要自行实现协议方法
@implementation Programmer
- (void)program {
    NSLog(@"I'm writing bugs!");
}
- (void)draw {
    NSLog(@"I can draw");
}
- (void)sing {
    NSLog(@"I can sing");
}
@end

#import "Programmer.h"

@interface Student : Programmer

@end

#import "Student.h"

@implementation Student
- (void)draw {
    NSLog(@"Student can draw");
}
- (void)sing {
    NSLog(@"Student can sing");
}
@end