外观模式定义
Facade模式也叫外观模式，是由
GoF提出的23种设计模式中的一种。
Facade模式为一组具有类似功能的类群，比如类库，子系统等等，提供一个一致的简单的界面。这个一致的简单的界面被称作facade
外部与一个子系统的通信必须通过一个统一的外观对象进行，为子系统中的一组接口提供一个一致的界面，外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用
属于结构型设计模式
菜鸟教程的介绍
简单的案例一
在一个系统中，往往完成一个功能需要多个子系统一同执行才能完成，比如录制视频，捕捉视频图像用到摄像头，捕捉音频要使用到麦。
class SubSystem1
{
public:
void run();
};
void SubSystem1::run()
{
cout << "子系统1运行" << endl;
}
class SubSystem2
{
public:
void run();
};
void SubSystem2::run()
{
cout << "子系统2运行" << endl;
}
class SubSystem3
{
public:
void run();
};
void SubSystem3::run()
{
cout << "子系统3运行" << endl;
}
class Facade{
private:
SubSystem1 *sys1;
SubSystem2 *sys2;
SubSystem3 *sys3;
public:
Facade();
~Facade();
void run();
};
Facade::Facade()
{
sys1 = new SubSystem1;
sys2 = new SubSystem2;
sys3 = new SubSystem3;
}
Facade::~Facade()
{
if (sys1 != NULL)
{
delete sys1;
}
if (sys2 != NULL)
{
delete sys2;
}
if (sys3 != NULL)
{
delete sys3;
}
}
void Facade::run() //三个子系统同时执行才能完成这个功能
{
sys1->run();
sys2->run();
sys3->run();
}
int main()
{
Facade *aFacade = new Facade;
aFacade->run();
delete aFacade;
return 0;
}
简单案例二
假设现有一家庭影院，有两种模式：
KTV模式：电视打开、灯关闭、音响打开、麦克风打开、DVD打开
游戏模式：电视打开、影响打开、游戏机打开、麦克风打开
void TV::turn_on(void)
{
cout << "电视打开" << endl;
}
void TV::turn_off(void)
{
cout << "电视关闭" << endl;
}
class Light
{
public:
void turn_on(void);
void turn_off(void);
};
void Light::turn_on(void)
{
cout << "灯打开" << endl;
}
void Light::turn_off(void)
{
cout << "灯关闭" << endl;
}
class Sound
{
public:
void turn_on(void);
void turn_off(void);
};
void Sound::turn_on(void)
{
cout << "音响打开" << endl;
}
void Sound::turn_off(void)
{
cout << "音响关闭" << endl;
}
class Microphone
{
public:
void turn_on(void);
void turn_off(void);
};
void Microphone::turn_on(void)
{
cout << "麦克风打开" << endl;
}
void Microphone::turn_off(void)
{
cout << "麦克风关闭" << endl;
}
class DVD
{
public:
void turn_on(void);
void turn_off(void);
};
void DVD::turn_on(void)
{
cout << "DVD打开" << endl;
}
void DVD::turn_off(void)
{
cout << "DVD关闭" << endl;
}
class Games
{
public:
void turn_on(void);
void turn_off(void);
};
void Games::turn_on(void)
{
cout << "游戏机打开" << endl;
}
void Games::turn_off(void)
{
cout << "游戏机关闭" << endl;
}
class KtvFacadeMode {
private:
TV *mTv;
DVD *mDvd;
Sound *mSound;
Light *mLight;
Microphone *mMic;
Games *mGames;
public:
KtvFacadeMode();
~KtvFacadeMode();
void run();
};
KtvFacadeMode::KtvFacadeMode()
{
mTv = new TV;
mDvd = new DVD;
mSound = new Sound;
mLight = new Light;
mMic = new Microphone;
mGames = new Games;
}
KtvFacadeMode::~KtvFacadeMode()
{
if (mTv != NULL){
delete mTv;
}
if (mDvd != NULL){
delete mDvd;
}
if (mSound != NULL){
delete mSound;
}
if (mLight != NULL) {
delete mLight;
}
if (mMic != NULL) {
delete mMic;
}
if (mGames != NULL){
delete mGames;
}
}
void KtvFacadeMode::run()
{
mTv->turn_on();
mLight->turn_off();
mSound->turn_on();
mMic->turn_on();
mDvd->turn_on();
}
class GameFacadeMode{
private:
TV *mTv;
DVD *mDvd;
Sound *mSound;
Light *mLight;
Microphone *mMic;
Games *mGames;
public:
GameFacadeMode();
~GameFacadeMode();
void run();
};
GameFacadeMode::GameFacadeMode()
{
mTv = new TV;
mDvd = new DVD;
mSound = new Sound;
mLight = new Light;
mMic = new Microphone;
mGames = new Games;
}
GameFacadeMode::~GameFacadeMode()
{
if (mTv != NULL) {
delete mTv;
}
if (mDvd != NULL){
delete mDvd;
}
if (mSound != NULL){
delete mSound;
}
if (mLight != NULL) {
delete mLight;
}
if (mMic != NULL) {
delete mMic;
}
if (mGames != NULL){
delete mGames;
}
}
void GameFacadeMode::run()
{
mTv->turn_on();
mLight->turn_on();
mSound->turn_on();
mGames->turn_on();
}
int main()
{
string modeSelect;
KtvFacadeMode *aKtvFacade = new KtvFacadeMode;
GameFacadeMode *aGameFacade = new GameFacadeMode;
while(1)
{
cin >> modeSelect;
if (modeSelect == "KTV")
{
aKtvFacade->run();
}
else if (modeSelect == "Game")
{
aGameFacade->run();
}
else
{
cout << "退出系统" << endl;
break;
}
}
delete aKtvFacade;
delete aGameFacade;
return 0;
}