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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

原则	说明
迪米特法则	一个对象应只与直接朋友交互，降低系统耦合
最少知识原则	客户端只需了解外观类，无需知道子系统细节

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

优点	缺点
简化客户端调用	可能增加外观类复杂度
降低子系统耦合	不符合开闭原则（修改外观类）
提高系统可维护性