【设计模式】外观模式

第8章 外观模式

8.1 配置相关范例

核心问题

游戏配置项复杂，直接调用业务类导致耦合度高：

1. 图形配置类

// 图形相关类
class Graphic {
private:
    // 单件模式实现
    Graphic() = default;
    Graphic(const Graphic&) = delete;
    Graphic& operator=(const Graphic&) = delete;
    ~Graphic() = default;

public:
    static Graphic& getInstance() {
        static Graphic instance;
        return instance;
    }

    // 图形配置接口
    void display(bool enable) {
        std::cout << "图形->是否全屏显示: " << (enable ? "是" : "否") << std::endl;
    }

    void effect(bool enable) {
        std::cout << "图形->是否开启特效: " << (enable ? "是" : "否") << std::endl;
    }

    void resolution(int index) {
        std::cout << "图形->分辨率设置: " 
                  << (index==0?"1920x1080":index==1?"1280x720":"1024x600") 
                  << std::endl;
    }

    void antialiasing(bool enable) {
        std::cout << "图形->是否开启抗锯齿: " << (enable ? "是" : "否") << std::endl;
    }
};

2. 声音配置类（单件模式）

// 声音相关类
class Sound {
private:
    // 单件模式实现
    Sound() = default;
    Sound(const Sound&) = delete;
    Sound& operator=(const Sound&) = delete;
    ~Sound() = default;

public:
    static Sound& getInstance() {
        static Sound instance;
        return instance;
    }

    // 声音配置接口
    void bgsound(bool enable) {
        std::cout << "声音->背景声音: " << (enable ? "开启" : "关闭") << std::endl;
    }

    void envirsound(bool enable) {
        std::cout << "声音->环境音效: " << (enable ? "开启" : "关闭") << std::endl;
    }

    void expsound(bool enable) {
        std::cout << "声音->表情声音: " << (enable ? "开启" : "关闭") << std::endl;
    }

    void setvolume(int level) {
        std::cout << "声音->音量设置: " << level << "%" << std::endl;
    }
};

3. 语音聊天类（单件模式）

// 语音聊天相关类
class ChatVoice {
private:
    // 单件模式实现
    ChatVoice() = default;
    ChatVoice(const ChatVoice&) = delete;
    ChatVoice& operator=(const ChatVoice&) = delete;
    ~ChatVoice() = default;

public:
    static ChatVoice& getInstance() {
        static ChatVoice instance;
        return instance;
    }

    // 语音配置接口
    void micvolume(int level) {
        std::cout << "语音->麦克风音量: " << level << "%" << std::endl;
    }

    void micsens(int level) {
        std::cout << "语音->麦克风灵敏度: " << level << "%" << std::endl;
    }

    void chatvolume(int level) {
        std::cout << "语音->聊天音量: " << level << "%" << std::endl;
    }
};

4. 客户端直接调用示例

int main() {
    // 图形配置
    Graphic& graphic = Graphic::getInstance();
    graphic.display(false);
    graphic.effect(true);
    graphic.resolution(1);
    graphic.antialiasing(true);

    std::cout << "------------------------" << std::endl;

    // 声音配置
    Sound& sound = Sound::getInstance();
    sound.bgsound(true);
    sound.envirsound(true);
    sound.expsound(false);
    sound.setvolume(75);

    std::cout << "------------------------" << std::endl;

    // 语音配置
    ChatVoice& chat = ChatVoice::getInstance();
    chat.micvolume(80);
    chat.micsens(60);
    chat.chatvolume(90);

    return 0;
}

8.2 外观模式实现

模式结构（Mermaid类图）

外观类实现

class ConfigFacade {
private:
    // 单件模式实现
    ConfigFacade() = default;
    ConfigFacade(const ConfigFacade&) = delete;
    ConfigFacade& operator=(const ConfigFacade&) = delete;
    ~ConfigFacade() = default;

public:
    static ConfigFacade& getInstance() {
        static ConfigFacade instance;
        return instance;
    }

    // 低配置方案
    void lowConfigSetup() {
        Graphic& g = Graphic::getInstance();
        g.display(true);    // 全屏降低资源消耗
        g.effect(false);    // 关闭特效
        g.resolution(2);    // 低分辨率
        g.antialiasing(false);

        Sound& s = Sound::getInstance();
        s.bgsound(false);
        s.envirsound(false);
        s.expsound(false);
        s.setvolume(15);

        ChatVoice& c = ChatVoice::getInstance();
        c.micvolume(20);
        c.micsens(50);
        c.chatvolume(60);
    }

    // 高配置方案
    void highConfigSetup() {
        Graphic& g = Graphic::getInstance();
        g.display(false);   // 窗口模式
        g.effect(true);     // 开启特效
        g.resolution(0);    // 最高分辨率
        g.antialiasing(true);

        Sound& s = Sound::getInstance();
        s.bgsound(true);
        s.envirsound(true);
        s.expsound(true);
        s.setvolume(50);

        ChatVoice& c = ChatVoice::getInstance();
        c.micvolume(100);
        c.micsens(100);
        c.chatvolume(100);
    }
};

客户端通过外观调用

int main() {
    ConfigFacade& facade = ConfigFacade::getInstance();
    
    std::cout << "【低配置电脑配置】" << std::endl;
    facade.lowConfigSetup();

    std::cout << "\n【高配置电脑配置】" << std::endl;
    facade.highConfigSetup();

    return 0;
}

8.3 家庭影院案例

系统架构（Mermaid组件图）

子系统实现

// 屏幕
class Screen {
public:
    void on() { std::cout << "屏幕升起" << std::endl; }
    void off() { std::cout << "屏幕降下" << std::endl; }
    void setInput(int input) { 
        std::cout << "设置输入源: " << (input==1?"HDMI":"AV") << std::endl;
    }
};

// 灯光
class Light {
public:
    void on() { std::cout << "灯光开启" << std::endl; }
    void off() { std::cout << "灯光关闭" << std::endl; }
    void dim(int level) { 
        std::cout << "灯光调暗至: " << level << "%" << std::endl;
    }
};

// 音箱
class Speaker {
public:
    void on() { std::cout << "音箱开启" << std::endl; }
    void off() { std::cout << "音箱关闭" << std::endl; }
    void setMode(int mode) {
        std::cout << "设置音效模式: " 
                  << (mode==1?"立体声":"环绕声") << std::endl;
    }
};

// DVD播放器
class DVDPlayer {
public:
    void on() { std::cout << "DVD播放器开启" << std::endl; }
    void off() { std::cout << "DVD播放器关闭" << std::endl; }
    void play(const std::string& movie) {
        std::cout << "播放电影: " << movie << std::endl;
    }
};

// 游戏机
class GameConsole {
public:
    void on() { std::cout << "游戏机开启" << std::endl; }
    void off() { std::cout << "游戏机关闭" << std::endl; }
    void loadGame(const std::string& game) {
        std::cout << "加载游戏: " << game << std::endl;
    }
};

外观类协调

class HomeTheaterFacade {
private:
    Screen screen;
    Light light;
    Speaker speaker;
    DVDPlayer dvd;
    GameConsole game;

public:
    void watchMovie(const std::string& movie) {
        // 观影模式
        std::cout << "\n=== 开始观影 ===" << std::endl;
        screen.on();
        screen.setInput(1);  // HDMI输入
        light.dim(20);
        speaker.on();
        speaker.setMode(2);  // 环绕声
        dvd.on();
        dvd.play(movie);
        game.off();
    }

    void playGame(const std::string& gameName) {
        // 游戏模式
        std::cout << "\n=== 开始游戏 ===" << std::endl;
        screen.on();
        screen.setInput(2);  // AV输入
        light.on();
        speaker.on();
        speaker.setMode(1);  // 立体声
        dvd.off();
        game.on();
        game.loadGame(gameName);
    }

    void shutdown() {
        // 关机流程
        std::cout << "\n=== 系统关闭 ===" << std::endl;
        screen.off();
        light.off();
        speaker.off();
        dvd.off();
        game.off();
    }
};

3. 客户端调用示例

int main() {
    HomeTheaterFacade theater;
    
    theater.watchMovie("《阿凡达2》");
    theater.playGame("《塞尔达传说》");
    theater.shutdown();

    return 0;
}

模式总结

核心原则

适用场景

1. 子系统复杂：存在多个独立子系统需要统一入口
2. 分层架构：需要为不同层次提供统一接口
3. 第三方库：封装底层API供上层调用

模式优缺点