协议的代理模式

#import <Foundation/Foundation.h>

@protocol TicketDelegate <NSObject>

//返回票价

- (double) ticketPrice;

//还剩多少张票

- (int) leftTicketsNumber;

@end

#import <Foundation/Foundation.h>

#import "TicketDelegate.h"

@interface Person : NSObject

@property (nonatomic,retain) id<TicketDelegate> delegate;

- (void) buyTicket;

//拥有一个代理属性

//id代表代理的类名随便

//但必须遵守TicketDelegate协议

@end

#import "Person.h"

@implementation Person

//买票

- (void) buyTicket

{

    //叫代理去帮自己买票

    double price = [_delegate ticketPrice];

    int number = [_delegate leftTicketsNumber];

     NSLog(@"通过代理的帮忙，票价=%f，还剩%d张票", price, number);

}

- (void)dealloc

{

    [_delegate release];

    [super dealloc];

}

@end

#import <Foundation/Foundation.h>

#import "TicketDelegate.h"

@interface Agent : NSObject <TicketDelegate>

@end

#import "Agent.h"

@implementation Agent

//剩余的票数

- (int)leftTicketsNumber

{

    return 1;

}

//每张票多少钱

- (double)ticketPrice

{

    return 100;

}

@end

#import <Foundation/Foundation.h>

#import "Person.h"

#import "TicketDelegate.h"

#import "Agent.h"

int main(int argc, const char * argv[]) {

    @autoreleasepool {

        // 创建一个Person类的对象

        Person *p = [[Person alloc] init];

        Agent *a = [[Agent alloc] init];

        p.delegate = a;

        [p buyTicket];

    }

    return 0;

}