iOS设计模式-代理

代理模式的原理

一个对象和另一个对象耦合，代理模式是为了降低耦合度

Customer & 使用代理的注意事项

1. @class, 提示协议方法有该类的引用
2. weak 防止循环引用
3. @required or @Optional 要写清楚

Customer

@class Customer;

@protocol CustomerDelegate <NSObject>

@required
- (void)custmer:(Customer *)custmer buyItemCount:(NSInteger)count;
@end

@interface Customer : NSObject

// 经销商
@property (nonatomic, weak) id <CustomerDelegate> delegate;

// 顾客买卖行为
- (void)buyItemCount:(NSInteger)count;
@end

- (void)buyItemCount:(NSInteger)count {
    if (self.delegate && [self.delegate respondsToSelector:@selector(custmer:buyItemCount:)]) {   
        [self.delegate custmer:self buyItemCount:count];
    }
}

ViewController

#import "ViewController.h"
#import "Customer.h"

// 经销商
@interface ViewController ()<CustomerDelegate>

- (void)viewDidLoad {
[super viewDidLoad];

Customer *customer  = [[Customer alloc] init];
customer.delegate   = self;  
[customer buyItemCount:5];
}

- (void)custmer:(Customer *)custmer buyItemCount:(NSInteger)count {   
NSLog(@"%ld", (long)count);
}

使用场景：用于类与类之间的值传递

Customer设定消息接受方的遵循条件

@required
- (void)custmer:(Customer *)custmer buyItemCount:(NSInteger)count;
@end

@interface Customer : NSObject

// 经销商
@property (nonatomic, weak) id <CustomerDelegate> delegate;

Customer发送消息

- (void)buyItemCount:(NSInteger)count {

    //代理存在，并且代理能响应这个方法

    if (self.delegate && [self.delegate respondsToSelector:@selector(custmer:buyItemCount:)]) {   
        [self.delegate custmer:self buyItemCount:count];
    }
}

ViewController准备接收

@interface ViewController ()<CustomerDelegate>

ViewController获得所传递的消息

Customer *customer  = [[Customer alloc] init];
customer.delegate   = self;  
[customer buyItemCount:5];
}

- (void)custmer:(Customer *)custmer buyItemCount:(NSInteger)count {   
NSLog(@"%ld", (long)count);
}

代理使用验证

//代理存在，并且代理能响应这个方法

if (self.delegate && [self.delegate respondsToSelector:@selector(custmer:buyItemCount:)]) {   
    [self.delegate custmer:self buyItemCount:count];
}

协议使用场景

约束对象，筛选对象。比如传递的对象，必须实现某种方法

协议

@protocol TCPProtocol <NSObject>
@required
// 获取源端口号
- (NSInteger)sourcePort;
// 获取目的地端口号
- (NSInteger)destinationPort;
@end

遵循协议的类

@interface Model : NSObject <TCPProtocol>
// 获取源端口号
- (NSInteger)sourcePort {
return 10;
}

// 获取目的地端口号
- (NSInteger)destinationPort {
return 20;
}

传递遵循协议的对象

- (void)accessTCPData:(id <TCPProtocol>)data { 
self.sourcePort      = [data sourcePort];
self.destinationPort = [data destinationPort];
}