iOS架构师_观察者模式

定义：

观察者模式（有时又被称为模型-视图（View）模式、源-收听者(Listener)模式或从属者模式），一个目标物件管理所有相依于它的观察者物件，并且在它本身的状态改变时主动发出通知。这通常透过呼叫各观察者所提供的方法来实现。此种模式通常被用来实现事件处理系统。

示例代码：自己实现观察者模式

创建Protocol类型的接口文件SubProtocol协议类

SubProtocol.h

#import <Foundation/Foundation.h>

@protocol SubProtocol <NSObject>

//用户的信息和从某一个刊物接收的信息
- (void)subMessage:(id)message withSubNumber:(NSString *)withSubNumber;
@end

创建观察中心SubCenter类
SubCenter.h

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

@interface SubCenter : NSObject
// 创建书刊订阅号
+ (void)creatNumber:(NSString *)subNumber;

// 移除订阅号
+ (void)removeNumber:(NSString *)subNumber;

// 添加用户
+ (void)addUser:(id <SubProtocol>)user wihtNumber:(NSString *)userNumber;

// 移除用户
+ (void)removeUser:(id <SubProtocol>)user withNumber:(NSString *)userNumber;

// 发送消息
+ (void)sendMessage:(id)message withSubNumber:(NSString *)SubNumber;

@end

SubCenter.m

//
//  SubCenter.m
//  观察者模式
//
//  Created by James on 2017/12/9.
//  Copyright © 2017年 TZ. All rights reserved.


#import "SubCenter.h"


static NSMutableDictionary *bookCenter = nil;
@implementation SubCenter

//单例
+ (void)initialize {
    if (self == [SubCenter class]) {
        bookCenter = [NSMutableDictionary dictionary];
    }
}

// 创建书刊订阅号
+ (void)creatNumber:(NSString *)subNumber {
    //  NSHashTable 就是一个集合,但是它是弱引用的.
    NSHashTable *hashTable = [self existNumber:subNumber];
    if (hashTable == nil) {
        hashTable = [NSHashTable weakObjectsHashTable];
        [bookCenter setObject:hashTable forKey:subNumber];
    }
}

// 移除订阅号
+ (void)removeNumber:(NSString *)subNumber {
    NSHashTable *hashTable = [self existNumber:subNumber];
    if (hashTable) {
        [bookCenter removeObjectForKey:subNumber];
    }
}

// 添加用户
+ (void)addUser:(id <SubProtocol>)user wihtNumber:(NSString *)userNumber {
    NSHashTable *hashTable = [self existNumber:userNumber];
    [hashTable addObject:user];
}

// 移除用户
+ (void)removeUser:(id <SubProtocol>)user withNumber:(NSString *)userNumber {
    NSHashTable *hashTable = [self existNumber:userNumber];
    [hashTable removeObject:user];
}

// 发送消息
+ (void)sendMessage:(id)message withSubNumber:(NSString *)SubNumber {
    NSHashTable *hashTable = [self existNumber:SubNumber];
    if (hashTable) {
        //构造器
        NSEnumerator *enumerato = [hashTable objectEnumerator];
        id <SubProtocol> object = nil;

        while (object = [enumerato nextObject]) {
            if ([object respondsToSelector:@selector(subMessage:withSubNumber:)]) {
                [object subMessage:message withSubNumber:SubNumber];
            }
        }

    }
}

#pragma mark - 私有方法
// 实现了代理方法
+ (NSHashTable *)existNumber:(NSString *)subStringNumber {
    return [bookCenter objectForKey:subStringNumber];
}

@end

ViewController调用

#import "ViewController.h"
#import "SubCenter.h"


static NSString *SCIENCE = @"SCIENCE";
@interface ViewController () <SubProtocol>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    // 创建订阅
    [SubCenter creatNumber:SCIENCE];

    // 添加订阅
    [SubCenter addUser:self wihtNumber:SCIENCE];

    // 发送消息
    [SubCenter sendMessage:@"11" withSubNumber:SCIENCE];
}

- (void)subMessage:(id)message withSubNumber:(NSString *)withSubNumber {
    NSLog(@"----%@----%@",message, withSubNumber);
}


@end