《设计模式：可复用面向对象软件的基础》学习并理解 23 种设计模式

 // 品牌
 @interface Brand : NSObject
 @interface Lenovo : Brand
 @interface Apple : Brand
 // CPU
 @interface CPU : NSObject
 @interface Inter : CPU
 @interface AMD : CPU

 @interface Computer : NSObject
 // 品牌
 @property (nonatomic, strong) Brand *brand;
 // CPU
 @property (nonatomic, strong) CPU *cpu;
 @end
 
 @interface Computer : NSObject
 @interface DesktopComputer : Computer
 @interface NotebookComputer : Computer

// 可乐抽象类
@interface Cola : NSObject
@end

// 可口可乐产品类
@interface CocaCola : Cola
@end

// 百事可乐产品类
@interface PesiCola : Cola
@end

// 简单工厂实现
@implementation SimpleFactory

+ (Cola *)createColaWithType:(NSInteger)type {
    switch (type) {
        case 0:
            return [CocaCola new];
        case 1:
            return [PesiCola new];
        default:
            return nil;
            break;
    }
}
@end

// 0 生产可口可乐
Cola *cocaCola = [SimpleFactory createColaWithType:0];

// 1 生产百事可乐
Cola *pesiCola = [SimpleFactory createColaWithType:1];

// 工厂抽象类
@implementation Factory
+ (Cola *)createCola {
    return [Cola new];
}
@end

// 可口可乐工厂
@implementation CocaColaFactory

+ (Cola *)createCola {
    return [CocaCola new];
}
@end

// 百事可乐工厂
@implementation PesiColaFactory
+ (Cola *)createCola {
    return [PesiCola new];
}
@end

// 根据不同的工厂类生产不同的产品
Cola *pesiCola = [PesiColaFactory createCola];
Cola *cocaCola = [CocaColaFactory createCola];

// 可乐抽象类和派生类
@interface Cola : NSObject
@end
@interface CocaCola : Cola
@end
@interface PesiCola : Cola
@end

// 瓶子抽象类和派生类
@interface Bottle : NSObject
@end
@interface CocaColaBottle : Bottle
@end
@interface PesiColaBottle : Bottle
@end

// 箱子抽象类和派生类
@interface Box : NSObject
@end
@interface CocaColaBox : Box
@end
@interface PesiColaBox : Box
@end

// 工厂抽象类
@implementation Factory

+ (Cola *)createCola {
    return [Cola new];
}
+ (Bottle *)createBottle {
    return [Bottle new];
}
+ (Box *)createBox {
    return [Box new];
}
@end

// 可口可乐主题工厂
@implementation CocaColaFactory

+ (CocaCola *)createCola {
    return [CocaCola new];
}
+ (CocaColaBottle *)createBottle {
    return [CocaColaBottle new];
}
+ (CocaColaBox *)createBox {
    return [CocaColaBox new];
}
@end

// 百事可乐主题工厂
@implementation PesiColaFactory
+ (PesiCola *)createCola {
    return [PesiCola new];
}
+ (PesiColaBottle *)createBottle {
    return [PesiColaBottle new];
}
+ (PesiColaBox *)createBox {
    return [PesiColaBox new];
}
@end

// 可口可乐主题
Cola *cocaCola = [CocaColaFactory createCola];
Bottle *cocaColaBottle = [CocaColaFactory createBottle];
Box *cocaColaBox = [CocaColaFactory createBox];

// 百事可乐主题
Cola *pesiCola = [PesiColaFactory createCola];
Bottle *pesiColaBottle = [PesiColaFactory createBottle];
Box *pesiColaBox = [PesiColaFactory createBox];

@implementation Singleton

+ (instancetype)shareInstance {
    static Singleton *shareInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        shareInstance = [[Singleton alloc] init];
    });
    return shareInstance;
}

@end

// 汽车生产器
@interface Builder : NSObject

+ (void)buildEngine;
+ (void)buildWheel;
+ (void)buildBody;

@end

// 创建过程进行拆分
Builder *builder = [Builder new];
[builder buildBody];
[builder buildWheel];
[builder buildEngine];

@interface Student : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *age;
@property (nonatomic, copy) NSString *class;
@property (nonatomic, copy) NSString *school;

@end

// 原对象
Student *lily = [Student alloc] init];
lily.name = @"lily";
lily.age = @"13";
lily.class = @"五年一班";
lily.school = @"实现学校";

// 复制原对象
Student *tom = [lily copy];

// 在原对象基础上微调
tom.name = @"tom";

@interface Tea : NSObject

+ (instancetype)createTea;

@end

@interface BlackTea : Tea

@property (nonatomic, strong) Tea *tea;

// 加红茶
- (void)addBlackTea;
// 红茶可以加柠檬
- (void)addLemon;

@end

@implementation Tea

+ (instancetype)createTea {
    NSLog(@"add water");
    return [self new];
}

@end

@implementation BlackTea
// 先加红茶，再加水
+ (instancetype)createTea {
    return [self new];
}

- (void)addBlackTea {
    NSLog(@"add black tea");
}

- (void)addLemon {
    NSLog(@"add lemon");
}

@end

// 茶
Tea *tea = [Tea createTea]; 
// output: add water

// 红茶
BlackTea *blackTea = [BlackTea createTea];
blackTea.tea = tea
[blackTea addBlackTea];
[blackTea addLemon];
// output: 
// add black tea 
// add lemon

@implementation WebImage

+ (UIImage *)getImageWithUrl:(NSString *)url {
    // 查看图片是否有缓存
    id cacheImage = [ImageCaches getImageFromCacheWithUrl:url];
    if (cacheImage) {
        return cacheImage;
    }
    
    // 下载图片
    id downloadImage = [ImageDownloader downloadImageWithUrl:url];
    if (downloadImage) {
      // 缓存图片
      [ImageCaches cacheImage:downloadImage];
      return downloadImage;
    }else{
      return nil;
    }
}
@end

@implementation UIImageView + WebImage / UIButton + WebImage

- (void)setImageWithUrl:(NSString *)url {
    UIImage webImage = [WebImage getImageWithUrl:url];
    if (webImage) {
      [self setImage:webImage];
    }
}
@end

// 使用的时候不需要关系内部缓存逻辑
UIImageView *webImage = [UIImageView new];
[webImage setImageWithUrl:@"https://imageUrl"];

UIButton *webButton = [UIButton new];
[webButton setImageWithUrl:@"https://imageUrl"];

// 顾客
@interface Customer ()

@property (nonatomic, strong) Waiter *waiter;

@end

@implementation Customer

// 叫服务生
- (Waiter *)callWaiter {
    _waiter = [Waiter new];
    return _waiter;
}

// 顾客点菜
- (void)orderingFood:(NSString *)food  {
    [_waiter orderingFood:food];
}

// 顾客取消某个菜
- (void)removeFood:(NSString *)food  {
    [_waiter removeFood:food];
}

@end

// 服务生
@interface Waiter ()

@property (nonatomic, strong) NSMutableArray *cacheList;

@end

@implementation Waiter

// 记下顾客点的菜
- (void)orderingFood:(NSString *)food  {
    [self.cacheList addObject:food];
}

// 帮助顾客取消某个菜
- (void)removeFood:(NSString *)food  {
    [self.cacheList removeObject:food];
}

// 将最早点的菜推给厨师
- (void)pushToChef:(Chef *)chef {
    [chef cookFood:self.cacheList.firstObject];
    [self.cacheList removeObject:self.cacheList.firstObject];
}

@end

// 厨师
@implementation Chef

- (void)cookFood:(NSString *)food {
    NSLog(@"cook %@",food);
}

@end

// 餐厅厨师
Chef *chef = [Chef new];

// 顾客
Customer *lily = [Customer new];
// 顾客叫服务生
[lily callWaiter];
// 顾客点餐
[lily orderingFood:@"小鸡炖蘑菇"];
[lily orderingFood:@"东坡肉"];
[lily orderingFood:@"虾饺皇"];
[lily orderingFood:@"红烧大虾"];
// 顾客取消某个菜
[lily removeFood:@"东坡肉"];

// 将最早点的菜菜推给厨师去烹饪
[waiter pushToChef:chef];

// 音乐服务
@interface MusicService ()

// 共享的音乐库
@property (nonatomic, strong) NSArray *musicLibrary;

@end

@implementation MusicService
// 听音乐
- (void)listenToMusct:(NSString *)music {
    ...
}
// 下载音乐
- (void)downloadMusic:(NSString *)music {
    ...
}

@end

// 免费音乐服务
@interface FreeMusicService : NSObject

@property (nonatomic, strong) MusicService *musicSever;

- (void)listenFreeMusic:(NSString *)music;

@end

@implementation FreeMusicService

// 只能听免费音乐
- (void)listenToFreeMusic:(NSString *)music {
    if ([music isEqualToString:@"free"]) {
      // 如果是免费则播放
        [self.musicSever listenMusct:music];
    }else{
      // 如果是收费音乐，则提示用户升级 Vip
        NSLog(@"please upgrade to Vip");
    }
}

@end


// Vip 音乐服务
@interface VipMusicService : NSObject

@property (nonatomic, strong) MusicService *musicSever;

- (void)listenMusic:(NSString *)music;

- (void)downloadMusic:(NSString *)music;

@end

@implementation VipMusicService

// 可以听全部的音乐
- (void)listenToMusic:(NSString *)music {
    [self.musicSever listenMusct:music];
}

// 可以下载音乐
- (void)downloadMusic:(NSString *)music {
    [self.musicSever downloadMusic:music];
}

@end

// 新建一个基础音乐库
MusicService *musicService = [MusicService new];

// 免费服务
FreeMusicService *freeService = [FreeMusicService new];
// 收费服务
VipMusicService *vipService = [VipMusicService new];

// 共享一个音乐库
freeService.musicSever = musicService;
vipService.musicSever = musicService;

[freeService listenFreeMusic:@"免费音乐"];
[vipService listenMusic:@"全部音乐"];

// 创建手机 SIM 卡协议
@protocol SIMCardProtocol <NSObject>
// 读取 SIM 卡信息接口
- (void)getSIMInfo;

@end

// SIM 卡抽象类
@interface SIMCard : NSObject
- (void)getSIMInfo;
@end

@implementation SIMCard
- (void)getSIMInfo {}
@end

// 联通 SIM 卡
@interface UnicomSIMCard : SIMCard<SIMCardProtocol>
@end

@implementation UnicomSIMCard
- (void)getSIMInfo {
    NSLog(@"Welcome Unicom User");
}
@end

// 移动 SIM 卡
@interface MobileSIMCard : SIMCard<SIMCardProtocol>
@end

@implementation MobileSIMCard
- (void)getSIMInfo {
    NSLog(@"Welcome Mobile User");
}
@end

// 手机抽象类
@interface Phone : NSObject
// 持有 SIM 卡
@property (nonatomic, strong) SIMCard *simCard;
// 启动手机方法
- (void)launchPhone;
@end

@implementation Phone
- (void)launchPhone {
    if (self.simCard) {
        [self.simCard getSIMInfo];
    }
}
@end

// iPhone
@interface iPhone : Phone
@end

// 小米手机
@interface miPhone : Phone
@end

// 联通卡
UnicomSIMCard *unicomSim = [UnicomSIMCard new];
// 移动卡
MobileSIMCard *mobileSim = [MobileSIMCard new];

// 小米手机安装上联调卡
miPhone *mi9 = [miPhone new];
[mi9 setSimCard:unicomSim];

// iPhone 安装上移动卡
iPhone *iPhoneX = [iPhone new];
[iPhoneX setSimCard:mobileSim];

// 开机
[mi9 launchPhone];
[iPhoneX launchPhone];

// 标准卡 尺寸协议
@protocol StandardSIMSizeProtocol <NSObject>
- (void)normalSize;
@end

// nano 卡尺寸协议
@protocol NanoSIMSizeProtocol <NSObject>
- (void)nanoSize;
@end

// 标准卡 遵循标准协议
@interface StandardSIMCard : SIMCard<StandardSIMSizeProtocol>
@end

@implementation StandardSIMCard
- (void)normalSize {}
@end

// nano 卡遵循 nano 协议
@interface NanoSIMCard : SIMCard<NanoSIMSizeProtocol>
@end

@implementation NanoSIMCard
- (void)nanoSize {}
@end

// Nano 卡套
@interface NanoAdapter : SIMCard<StandardSIMSizeProtocol>
@property (nonatomic, strong) NanoSIMCard *nanoSIMCard;
@end

@implementation NanoAdapter
- (void)normalSize {}
@end

// 
@interface OnePhone : Phone

- (void)setSimCard:(SIMCard *)simCard;

@end

@implementation OnePhone
- (void)setSimCard:(SIMCard *)simCard {
    [simCard normalSize];
}
@end

// 标准卡
StandardSIMCard *standardCard = [StandardSIMCard new];
// Nano 卡
NanoSIMCard *nanoCard = [NanoSIMCard new];

// 创建大卡槽手机 插入卡后会调用 normalSize() 方法
OnePhone *onePhone = [OnePhone new];

// 标准卡 遵循 StandardSIMSizeProtocol，协议 实现了 normalSize() 方法
[onePhone setSimCard:standardCard];

// Nano 遵循 NanoSIMSizeProtocol 协议，并没有实现了 normalSize() 方法，所以会报错
[onePhone setSimCard:nanoCard];

// 加一个 Nano 卡套
NanoAdapter *nanoAdapter = [NanoAdapter new];
// 卡套持有 Nano 卡实例，方便获取 Nano 卡信息
nanoAdapter.nanoSIMCard = nanoCard;
// 将卡套放入手机， 卡套遵循 StandardSIMSizeProtocol，实现了 normalSize() 方法
[onePhone setSimCard:nanoAdapter];

// 响应者
@interface Responder : NSObject

@property (nonatomic, strong) Responder *nextResponder;
@property (nonatomic, strong) NSString *name;
@property (nonatomic, assign) NSUInteger UpperLimit;
@property (nonatomic, assign) NSUInteger LowerLimit;

- (void)respondWithCode:(NSUInteger)code;

@end

@implementation Responder

- (void)respondWithCode:(NSUInteger)code {
    if (_LowerLimit <= code && code <= _UpperLimit) {
      // 在处理范围内 
        NSLog(@"code: %ld is %@", code, _name);
    }else if (_nextResponder){
      // 不在处理范围则 传递给下一位响应者
        [_nextResponder respondWithCode:code];
    }else{
      // 响应链结束
        NSLog(@"code: %ld no match responder", code);
    }
}

@end

// 建立响应链
Responder *successResponder = [Responder new];
Responder *warmingResponder = [Responder new];
Responder *httpResponder = [Responder new];
Responder *serviceResponder = [Responder new];

successResponder.nextResponder = warmingResponder;
warmingResponder.nextResponder = httpResponder;
httpResponder.nextResponder = serviceResponder;

// 设置处理范围
successResponder.LowerLimit = 200;
successResponder.UpperLimit = 299;
successResponder.name = @"success";

warmingResponder.LowerLimit = 300;
warmingResponder.UpperLimit = 399;
warmingResponder.name = @"warming";

httpResponder.LowerLimit = 400;
httpResponder.UpperLimit = 499;
httpResponder.name = @"http fail";

serviceResponder.LowerLimit = 500;
serviceResponder.UpperLimit = 599;
serviceResponder.name = @"service fail";

// 使用响应者链
[successResponder respondWithCode:200]; // code: 200 is success
[successResponder respondWithCode:310]; // code: 310 is warming
[successResponder respondWithCode:401]; // code: 401 is http fail
[successResponder respondWithCode:555]; // code: 555 is service fail
[successResponder respondWithCode:666]; // code: 666 no match responder

// 命令 -> 按钮
@interface Command : NSObject

@property (nonatomic, assign) SEL sel;
@property (nonatomic, strong) NSObject *target;

- (void)execute;
@end

@implementation Command

- (void)execute {
    [self.target performSelector:_sel withObject:nil];
}

@end

// 调用者 -> 遥控器
@interface Controller : NSObject

// 执行命令
- (void)invokCommand:(Command *)command;
// 取消命令
- (void)cancelCommand:(Command *)command;
@end

@implementation Controller

- (void)invokCommand:(Command *)command {
    [command execute];
}

- (void)cancelCommand:(Command *)command {
}

@end

// 接收者 -> 电视
@interface TV : NSObject

- (void)turnOn;

- (void)turnOff;
@end

@implementation TV

- (void)turnOn {
    NSLog(@"trun on");
}

- (void)turnOff {
    NSLog(@"trun off");
}

@end

// 接收者
TV *tv = [TV new];

// 定义命令 可以定义一个命令抽象类然后派生出各种命令类，这里作者就偷个懒了
Command *turnOnCommand = [Command new];
turnOnCommand.sel = @selector(turnOn); // 开电视命令
turnOnCommand.target = tv;

Command *turnOffCommand = [Command new];
turnOffCommand.sel = @selector(turnOff); // 关电视命令
turnOffCommand.target = tv;

// 调用者
Controller *controller = [Controller new];

// 调用者直接调用命令，不接触接收者
[controller invokCommand:turnOnCommand]; // trun on
[controller invokCommand:turnOffCommand]; // trun off

// 在此基础上也可以拓展出取消命令 cancelCommand 等方法就不一一列举

// 数据列表
@interface List : NSObject

@property (nonatomic, strong) NSArray *list;

@end

@implementation List

- (instancetype)init
{
    self = [super init];
    if (self) {
      // 原始数据
        _list = @[@"0",@"1",@"2",@"3",@"4",@"5"];
    }
    return self;
}

@end

// 迭代器
@interface Iterator : NSObject

@property (nonatomic, assign) NSUInteger index;

- (NSString *)previous; // 上一个数据
- (NSString *)next; // 下一个数据
- (BOOL)isFirst; // 当前是否为第一个数据

@end

@interface Iterator ()

// 迭代器持有数据源
@property (nonatomic, strong) List *list;

@end

@implementation Iterator

- (instancetype)init
{
    self = [super init];
    if (self) {
        _list = [List new];
    }
    return self;
}

- (NSString *)previous {
    _index = MAX(0, _index - 1);
    return [_list.list objectAtIndex:_index];
}

- (NSString *)next {
    _index = MIN(_list.list.count-1, _index + 1);
    return [_list.list objectAtIndex:_index];
}

- (BOOL)isFirst {
    return _index == 0;
}

@end

// 使用迭代器输出数据
Iterator *iterator = [Iterator new];
NSLog(@"%@",[iterator next]); // 1
NSLog(@"%@",[iterator next]); // 2
NSLog(@"%@",[iterator next]); // 3
NSLog(@"%@",[iterator previous]); // 2

// 聊天室中介者
@interface ChatMediator : NSObject

+ (instancetype)shareMediator;
// 聊天室成员注册
- (void)registerChatMember:(ChatMember *)chatMember;
// 转发消息
- (void)forwardMsg:(NSString *)msg fromMember:(ChatMember *)fromMember;

@end

@interface ChatMediator ()

@property (nonatomic, strong) NSMutableArray *memberList; // 已注册成员列表

@end

@implementation ChatMediator

+ (instancetype)shareMediator {
    static ChatMediator *shareInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        shareInstance = [[ChatMediator alloc] init];
    });
    return shareInstance;
}

- (instancetype)init
{
    self = [super init];
    if (self) {
        _memberList = [[NSMutableArray alloc] init];
    }
    return self;
}

- (void)registerChatMember:(ChatMember *)chatMember {
    [_memberList addObject:chatMember];
}

- (void)forwardMsg:(NSString *)msg fromMember:(ChatMember *)fromMember {
    [_memberList enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        ChatMember *member = obj;
        if (member != fromMember) [member receiveMsg:msg fromMember:member];
    }];
}

@end

// 聊天室成员
@interface ChatMember : NSObject

@property (nonatomic, strong) NSString *userName; // 成员昵称
// 发送消息
- (void)sendMsg:(NSString *)msg;
// 接收消息
- (void)receiveMsg:(NSString *)msg fromMember:(ChatMember *)fromMember;

@end

@implementation ChatMember

- (void)sendMsg:(NSString *)msg {
    [[ChatMediator shareMediator] forwardMsg:msg fromMember:self];
}

- (void)receiveMsg:(NSString *)msg fromMember:(ChatMember *)fromMember {
    NSLog(@"%@ receive: %@ from %@", _userName, msg, fromMember.userName);
}

@end

// 聊天室中介者
ChatMediator *mediator = [ChatMediator shareMediator];
// 新建聊天室成员
ChatMember *lily = [ChatMember new];
ChatMember *tom = [ChatMember new];
ChatMember *jack = [ChatMember new];
// 成员在中介者处注册
[mediator registerChatMember:lily];
[mediator registerChatMember:tom];
[mediator registerChatMember:jack];
// 命名
lily.userName = @"lily";
tom.userName = @"tom";
jack.userName = @"jack";
// 发送消息
[lily sendMsg:@"hello everyone!"];
[tom sendMsg:@"hello lily!"];
[jack sendMsg:@"hi tom!"];

输出：
tom receive: hello everyone! from lily
jack receive: hello everyone! from lily
lily receive: hello lily! from tom
jack receive: hello lily! from tom
lily receive: hi tom! from jack
tom receive: hi tom! from jack

// 角色状态
@interface PlayerState : NSObject

@property (nonatomic, strong) NSString *name;
@property (nonatomic, assign) NSUInteger level;
@property (nonatomic, assign) NSUInteger rank;

@end

@implementation PlayerState@end

// 角色类
@interface Player : NSObject

@property (nonatomic, strong) PlayerState *state; // 角色状态

// 设置角色状态
- (void)setPlayerName:(NSString *)name level:(NSUInteger)level rank:(NSUInteger)rank;

@end

@implementation Player
- (void)setPlayerName:(NSString *)name level:(NSUInteger)level rank:(NSUInteger)rank {
    if (!_state) _state = [PlayerState new];
    _state.name = name;
    _state.level = level;
    _state.rank = rank;
}
@end

// 备忘录
@interface Memorandum : NSObject

// 存储
- (void)storeWithPlayer:(Player *)player;
// 恢复
- (void)restoreWithPlayer:(Player *)player;

@end


@interface Memorandum ()

@property (nonatomic, strong) PlayerState *state; // 备忘录存储的角色状态

@end

@implementation Memorandum

- (void)storeWithPlayer:(Player *)player {
    _state = player.state;
}

- (void)restoreWithPlayer:(Player *)player {
    if(_state) player.state = _state;
}

@end

// 创建角色 A
Player *playA = [Player new];
[playA setPlayerName:@"King" level:99 rank:30];

// 创建备忘录并保存角色 A 的状态
Memorandum *memorandum = [Memorandum new];
[memorandum storeWithPlayer:playA];

// 创建角色 B 并使用备忘录恢复状态
Player *playB = [Player new];
[memorandum restoreWithPlayer:playB];
NSLog(@"name:%@ level:%ld rank:%ld", playB.state.name, playB.state.level, playB.state.rank);

输出：name:King level:99 rank:30

// 观察目标 - 气象站
@interface WeatherStation : NSObject

@property (nonatomic, strong) NSString *state; // 天气状态

// 观察者注册方法
- (void)registerWithObserver:(Observer *)observer;

@end

@interface WeatherStation ()

@property (nonatomic, strong) NSMutableArray *observerList;

@end

@implementation WeatherStation

- (instancetype)init
{
    self = [super init];
    if (self) {
        [self addObserver:self forKeyPath:@"state" options:NSKeyValueObservingOptionNew context:nil];
    }
    return self;
}

- (void)dealloc {
    [self removeObserver:self forKeyPath:@"state"];
}

// 目标状态改变监听事件
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    NSString *state = change[@"new"];
    [_observerList enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        Observer *ob = obj;
        [ob observeWeather:state];
    }];
}

// 观察者注册方法
- (void)registerWithObserver:(Observer *)observer {
    if (!_observerList) _observerList = [NSMutableArray new];
    [_observerList addObject:observer];
}

@end

// 观察者
@interface Observer : NSObject

@property (nonatomic, strong) NSString *name; // 观察者名字
// 被通知方法
- (void)observeWeather:(NSString *)weather;

@end

@implementation Observer

- (void)observeWeather:(NSString *)weather {
    NSLog(@"%@ observe weather changed: %@", _name, weather);
}

@end

// 新建监听目标 - 气象站
WeatherStation *station = [WeatherStation new];
// 新建监听者
Observer *farmer = [Observer new];
Observer *student = [Observer new];
farmer.name = @"farmer";
student.name = @"student";

// 监听者注册
[station registerWithObserver:farmer];
[station registerWithObserver:student];

// 改变状态
station.state = @"rainy";
station.state = @"sunny";

输出：
farmer observe weather changed: rainy
student observe weather changed: rainy
farmer observe weather changed: sunny
student observe weather changed: sunny

// 账户状态抽象类
@interface State : NSObject
// 存钱
- (BOOL)saveMoney:(float)money;
// 取钱
- (BOOL)drawMoney:(float)money;
// 借钱
- (BOOL)borrowMoney:(float)money;

@end

@implementation State

- (BOOL)saveMoney:(float)money {
    return NO;
}

- (BOOL)drawMoney:(float)money {
   return NO;
}

- (BOOL)borrowMoney:(float)money {
   return NO;
}

@end

// 存款富余状态
@interface RichState : State
@end

@implementation RichState
// 存钱
- (BOOL)saveMoney:(float)money {
    NSLog(@"欢迎存钱 %.2f", money);
    return YES;
}
// 取钱
- (BOOL)drawMoney:(float)money {
    NSLog(@"欢迎取钱 %.2f", money);
    return YES;
}
// 借钱
- (BOOL)borrowMoney:(float)money {
    NSLog(@"您还有余额，请先花完余额");
    return NO;
}

@end

// 零存款零负债状态
@interface ZeroState : State
@end

@implementation ZeroState
// 存钱
- (BOOL)saveMoney:(float)money {
    NSLog(@"欢迎存钱 %.2f", money);
    return YES;
}
// 取钱
- (BOOL)drawMoney:(float)money {
    NSLog(@"您当前没有余额");
    return NO;
}
// 借钱
- (BOOL)borrowMoney:(float)money {
    NSLog(@"欢迎借钱 %.2f", money);
    return YES;
}

@end

// 负债状态
@interface DebtState : State
@end

@implementation DebtState
// 存钱
- (BOOL)saveMoney:(float)money {
    NSLog(@"欢迎还钱 %.2f", money);
    return YES;
}
// 取钱
- (BOOL)drawMoney:(float)money {
    NSLog(@"您当前没有余额");
    return NO;
}
// 借钱
- (BOOL)borrowMoney:(float)money {
    NSLog(@"上次欠的账还没有还清，暂时无法借钱");
    return NO;
}

@end

// 银行账户类
@interface Account : NSObject
// 存钱
- (void)saveMoney:(float)money;
// 取钱
- (void)drawMoney:(float)money;
// 借钱
- (void)borrowMoney:(float)money;

@end

@interface Account ()

@property (nonatomic, assign) float money; // 余额
@property (nonatomic, strong) State *state; // 账户状态

@end

@implementation Account

// 初始化账户
- (instancetype)init
{
    self = [super init];
    if (self) {
        _money = 0;
        _state = [ZeroState new];
    }
    return self;
}

// 存钱
- (void)saveMoney:(float)money {
    if ([_state saveMoney:money]) {
        _money += money;
        [self updateState];
    }
    NSLog(@"余额：%.2f", _money);
}
// 取钱
- (void)drawMoney:(float)money {
    if ([_state drawMoney:money]) {
        _money -= money;
        [self updateState];
    }
    NSLog(@"余额：%.2f", _money);
}
// 借钱
- (void)borrowMoney:(float)money {
    if ([_state borrowMoney:money]) {
        _money -= money;
        [self updateState];
    }
    NSLog(@"余额：%.2f", _money);
}

// 更新账户状态
- (void)updateState {
    if (_money > 0) {
        _state = [RichState new];
    }else if (_money == 0) {
        _state = [ZeroState new];
    }else{
        _state = [DebtState new];
    }
}

@end

// 初始化银行账户
Account *bankAccount = [Account new];
// 取 50
[bankAccount drawMoney:50]; // 余额：0 您当前没有余额
// 存 100
[bankAccount saveMoney:100]; // 余额：0 欢迎存钱 100.00
// 借 100
[bankAccount borrowMoney:100]; // 余额：100 您还有余额，请先花完余额
// 取 100
[bankAccount drawMoney:100]; // 余额：100 欢迎取钱 100.00
// 借 100
[bankAccount borrowMoney:100]; // 余额：0 欢迎借钱 100.00
// 借 50
[bankAccount borrowMoney:50]; // 余额：-100 上次欠的账还没有还清，暂时无法借钱

// Vip  - 销售策略抽象类
@interface Vip : NSObject

// vip 折扣
- (float)getDiscount;
// vip 所需邮费
- (float)getPostage;
// 根据折扣和邮费计算价格
- (float)calcPrice:(float)price;

@end

@implementation Vip

- (float)getDiscount {
    return 1;
}

- (float)getPostage {
    return 20;
}

- (float)calcPrice:(float)price {
    float payPrice = price*[self getDiscount] + [self getPostage];
    return payPrice;
}

@end

// 青铜 vip - 具体策略类
@interface BronzeVip : Vip
@end

@implementation BronzeVip

- (float)getDiscount {
    return 0.9;
}

- (float)getPostage {
    return 20;
}

@end

// 白银 vip
@interface SilverVip : Vip
@end

@implementation SilverVip

- (float)getDiscount {
    return 0.7;
}

- (float)getPostage {
    return 10;
}

@end

// 黄金 vip
@interface GoldVip : Vip
@end

@implementation GoldVip

- (float)getDiscount {
    return 0.5;
}

- (float)getPostage {
    return 0;
}

@end

// 线上商城 - 环境类
@interface OnlineShop : NSObject

// 购买商品 传入持有的 vip 卡
- (void)buyProductWithVip:(Vip *)vip;

@end

@implementation OnlineShop

- (void)buyProductWithVip:(Vip *)vip {
    float productPrice = 100;
    float payPrice = [vip calcPrice:productPrice];
    NSLog(@"pay: %f", payPrice);
}

@end

// 初始化商城类
OnlineShop *shop = [OnlineShop new];
// 新建各种 vip
GoldVip *goldVip = [GoldVip new];
SilverVip *silverVip = [SilverVip new];
BronzeVip *bronzeVip = [BronzeVip new];

// 使用青铜 vip 购买 100 元的商品
[shop buyProductWithVip:bronzeVip]; // 9折+20运费 pay: 110.00
// 使用白银 vip 购买 100 元的商品
[shop buyProductWithVip:silverVip]; // 7折+10运费 pay: 80.00
// 使用黄金 vip 购买 100 元的商品
[shop buyProductWithVip:goldVip]; // 5折+ 0运费 pay: 50.00

// 烹饪教程 模板方法类
@interface CookTutorial : NSObject

// 烹饪食物 - 具体方法
- (void)cook;
// 准备食材 - 抽象方法
- (void)prepareIngredients;
// 加食用油 具体方法
- (void)addFat;
// 加入食材 - 抽象方法
- (void)addIngredients;
// 加入调味品 - 具体方法
- (void)addFlavouring;
// 是否为健康食物 - 钩子方法
- (BOOL)isHealthyFood;

@end

@implementation CookTutorial

- (void)cook {
    [self prepareIngredients];
    // 如果是健康食物不加食用油
    if (![self isHealthyFood]) {
        [self addFat];
    }
    [self addIngredients];
    [self addFlavouring];
}

// 抽象方法
- (void)prepareIngredients {}

// 具体方法
- (void)addFat {
    NSLog(@"2. 加调和油");
}

// 抽象方法
- (void)addIngredients {}

// 具体方法
- (void)addFlavouring {
    NSLog(@"4. 加盐");
}

//  钩子方法
- (BOOL)isHealthyFood {
    return NO;
}

@end

// 烹饪 ? - 模板方法子类
@interface CookFish : CookTutorial
@end

@implementation CookFish

// 准备食材
- (void)prepareIngredients {
    NSLog(@"1. 准备好生鳕鱼");
}

// 加入食材
- (void)addIngredients {
    NSLog(@"3. 生鳕鱼入锅");
}

// 加入调味品
- (void)addFlavouring {
    [super addFlavouring];
    NSLog(@"4. 加黑胡椒");
}

// 是否为健康食物（不放油）
- (BOOL)isHealthyFood {
    return YES;
}

@end

CookFish * cookFish = [CookFish new];
[cookFish cook]; 
输出：
1. 准备好生鳕鱼
3. 生鳕鱼入锅
4. 加盐
4. 加黑胡椒

// 部门抽象类 - 访问者抽象类
@interface Department : NSObject
// 访问抽象方法 用来声明方法
- (void)visitEmployee:(Employee *)employee;

@end

@implementation Department

- (void)visitEmployee:(Employee *)employee {}

@end

// 财务部门 - 具体访问者类
@interface FADepartment : Department
@end

@implementation FADepartment
// 访问具体方法
- (void)visitEmployee:(Employee *)employee {
    if (employee.workTime > 40) {
        NSLog(@"%@ 工作时间满 40 小时", employee.name);
    }else{
        NSLog(@"%@ 工作时间不满 40 小时，要警告！", employee.name);
    }
}

@end

// HR 部门 - 具体访问者类
@interface HRDepartment : Department
@end

@implementation HRDepartment
// 访问具体方法
- (void)visitEmployee:(Employee *)employee {
    NSUInteger weekSalary = employee.workTime * employee.salary;
    NSLog(@"%@ 本周获取薪资：%ld",employee.name , weekSalary);
}

@end

// 抽象雇员类 - 被访问者抽象类
@interface Employee : NSObject
// 姓名
@property (nonatomic, strong) NSString *name;
// 工作时间
@property (nonatomic, assign) NSUInteger workTime;
// 时薪
@property (nonatomic, assign) NSUInteger salary;
// 接受访问抽象方法
- (void)accept:(Department *)department;

@end

@implementation Employee

- (void)accept:(Department *)department {}

@end

// 雇员具体类 - 被访问者具体类
@interface FulltimeEmployee : Employee

@end

@implementation FulltimeEmployee
// 接受访问具体方法
- (void)accept:(Department *)department {
    [department visitEmployee:self];
}

@end

// 新建财务和 HR - 访问者
FADepartment *fa = [FADepartment new];
HRDepartment *hr = [HRDepartment new];

// 新建雇员 - 被访问者
FulltimeEmployee *tim = [FulltimeEmployee new];
tim.name = @"tim";
tim.workTime = 55;
tim.salary = 100;

FulltimeEmployee *bill = [FulltimeEmployee new];
bill.name = @"bill";
bill.workTime = 38;
bill.salary = 150;

// 一般被访问者都存储在数据集合中方便遍历，集合中可以存储不同类型的被访问者
NSArray *employeeList = @[tim, bill];
[employeeList enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    Employee *employee = obj;
    // 接受财务访问
    [employee accept:fa];
    // 接受 HR 访问
    [employee accept:hr];
}];

输出：
tim 工作时间满 40 小时
tim 本周获取薪资：5500
bill 工作时间不满 40 小时，要警告！
bill 本周获取薪资：5700