设计模式--代理

通过协议实现代理设计模式。它的作用在于，一个雷需要实现特定的功能时，不需要专门自己去实现，可以由特定的类去帮忙实现。这个类可以根据功能的不同而去修改。

所以代理的好处在于

解耦合

下面用个冰箱 制冷协议来模拟一下代理模式：

制冷协议：

//
//  FreezeProtocol.h
//
//
//  Created by hhg on 15-6-16.
//  Copyright (c) 2015年 hhg. All rights reserved.
//

#import <Foundation/Foundation.h>

@protocol FreezeProtocol <NSObject>

/// 制冷
-(void)refrigeration;

@end

冰箱：

#import <Foundation/Foundation.h>
#import "FreezeProtocol.h"

@interface Refrigerator : NSObject<FreezeProtocol>

@end

//
//  Refrigerator.m
//
//
//  Created by hhg on 15-6-16.
//  Copyright (c) 2015年 hhg. All rights reserved.
//

#import "Refrigerator.h"

@implementation Refrigerator

-(void)refrigeration {
    NSLog(@"冷藏食物");
}

@end

使用冰箱的人

//
//  Person.h
//
//
//  Created by hhg on 15-6-16.
//  Copyright (c) 2015年 hhg. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "FreezeProtocol.h"

@interface Person : NSObject

@property (nonatomic,strong)id <FreezeProtocol>refrigeratorDelegate;

- (void)toFreezeSome;
@end

//
//  Person.m
//
//
//  Created by hhg on 15-6-16.
//  Copyright (c) 2015年 hhg. All rights reserved.
//
#import "Person.h"

@implementation Person

- (void)toFreezeSome {
    NSLog(@"想吃点冷的东西，拿食物去制冷");
    [_refrigeratorDelegate refrigeration];
}

@end

调用：

//
//  main.m
//
//
//  Created by hhg on 15-6-16.
//  Copyright (c) 2015年 hhg. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Refrigerator.h"
#import "Person.h"

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

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

        Refrigerator *myRefrigerator = [[Refrigerator alloc]init];

        [me setRefrigeratorDelegate:myRefrigerator];

        [me toFreezeSome];


    }
    return 0;
}

当我们需要界面间反向传值时，也可以使用代理模式传值。
先来个传值协议

//
//  DataProtocol.h
//  DataProtocol
//
//  Created by hhg on 2018/6/3.
//  Copyright © 2018年 hhg. All rights reserved.
//

#import <Foundation/Foundation.h>

@protocol DataProtocol <NSObject>

-(void)postValue:(NSString *)string;

@end

找个代理

//
//  NextViewController.h
//  DataProtocol
//
//  Created by hhg on 15/9/21.
//  Copyright © 2015年 hhg. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "DataProtocol.h"
@interface NextViewController : UIViewController

@property (nonatomic,strong)id<DataProtocol>Delegate;

@end

//
//  NextViewController.m
//  DataProtocol
//
//  Created by hhg on 15/9/21.
//  Copyright © 2015年 hhg. All rights reserved.
//

#import "NextViewController.h"

@implementation NextViewController

-(void)viewDidLoad {
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];
    NSArray *arr = [[NSArray alloc]initWithObjects:@"A",@"B",@"C",@"D", nil];
    for (NSUInteger i = 1 ; i < 5 ; i++) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        button.frame = CGRectMake(100, 300 + (i - 1) * 40, 80, 30);
        button.backgroundColor = [UIColor colorWithRed:(arc4random() % 256 / 255.) green:(arc4random() % 256 / 255.) blue:(arc4random() % 256 / 255.) alpha:1];
        [self.view addSubview:button];

        [button setTitle:arr[i - 1] forState:UIControlStateNormal];
        [button addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];

    }
}

-(void)buttonClick:(UIButton *)button {

    [self.Delegate postValue:button.titleLabel.text];

    [self dismissViewControllerAnimated:YES completion:nil];
}
@end

委托代理实现反向传值

//
//  RootViewController.h
//  DataProtocol
//
//  Created by hhg on 15/9/21.
//  Copyright © 2015年 hhg. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "DataProtocol.h"

@interface RootViewController : UIViewController<DataProtocol> {
    UILabel *label;
}
@end

//
//  RootViewController.m
//  DataProtocol
//
//  Created by hhg on 15/9/21.
//  Copyright © 2015年 hhg. All rights reserved.
//

#import "RootViewController.h"
#import "NextViewController.h"

@implementation RootViewController

-(void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];

    label = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
    label.backgroundColor = [UIColor grayColor];
    label.text=@"label";
    [self.view addSubview:label];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake(200, 200, 100, 100);
    button.backgroundColor=[UIColor blueColor];

    [button setTitle:@"下一页" forState:UIControlStateNormal];
    [self.view addSubview:button];
    [button addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];

}

// 协议方法
-(void)postValue:(NSString *)string {
    label.text = string;
}

-(void)buttonClick:(UIButton *)button {

    NextViewController *next = [[NextViewController alloc]init];
    next.Delegate = self;
    [self presentViewController:next animated:YES completion:nil];

}
@end