oc - 协议 protocol

@protocol myProtocol <NSObject> // 基协议

@required // 声明了必须要实现的，默认情况下都是          

@required

- (void)walk;

- (void)speak;

- (void)think; // think在类实现中未实现会警告!!!

@optional

- (void)sing;

- (void)laugh;

@end

协议可以声明一大堆方法，但不能声明成员变量；

两个协议之间不能继承，但协议可以遵守另一个协议；

子类可以遵守父类遵守的协议；

NSObject<myProtocol,allProtocol> * stu = [[Student alloc]init];

等价于

Student *stu = [[Student alloc]init];// 任何类

   [stu eat]; // 子类重写了，调用子类的

   [stu run]; // 子类没重写，向上找找到父类的方法

student can eat

person can run

Program ended with exit code: 0

Student * stu  = [[Student alloc]init];

Student <myProtocol>  * student = stu;

NSObject<myProtocol> * student = stu；

id<myProtocol> student = stu;

若报错，就检验出stu没遵守协议

#import "Student.h"

@implementation Student

- (void)exam{

    NSLog(@"student can exam.");

}

- (void)eat{

    NSLog(@"student can eat");

}

@end

#import <Foundation/Foundation.h>

@protocol allProtocol <NSObject>

- (void)eat;

- (void)run;

@end

#import "Person.h"

@implementation Person

- (void)eat{

    NSLog(@"person can eat");

}

- (void)run{

    NSLog(@"person can run");

}

@end

oc - 协议 protocol

原文：http://www.cnblogs.com/qq343351666/p/4404864.html