大话设计模式（11）——桥接模式（Bridge）_bridge abstraction

桥接模式（Bridge）

桥接模式（Bridge）：将抽象部分(Abstraction)与它的实现部分(Implementation)分离，使它们都可以独立地变化。
什么叫抽象与它的实现分离，这并不是说，让抽象类与其派生类分离，因为这样没有任何意义。实现指的是抽象类和它的派生类用来实现自己的对象。

手机品牌和手机软件的关系
手机品牌包含手机软件，但是软件并不是品牌的一部分，所以他们之间是聚合关系。

#include <iostream>
using namespace std;

class HandsetSoft {
public:
	virtual void run() = 0;
};
class HandsetGame :public HandsetSoft {
public:
	void run() {
		cout << "运行手机游戏" << endl;
	}
};
class HandsetAddressList :public HandsetSoft {
public:
	void run() {
		cout << "运行手机通讯录" << endl;
	}
};

class HandsetBrand {
protected:
	HandsetSoft* soft = nullptr;
public:
	void setHandsetSoft(HandsetSoft* soft) {
		this->soft = soft;
	}
	virtual void run() = 0;
};
class HandsetBrandN :public HandsetBrand {
public:
	void run() {
		soft->run();
	}
};
class HandsetBrandM :public HandsetBrand {
public:
	void run() {
		soft->run();
	}
};

int main() {
	HandsetBrand* hb = new HandsetBrandM();
	hb->setHandsetSoft(new HandsetGame());
	hb->run();
	hb->setHandsetSoft(new HandsetAddressList());
	hb->run();

	delete hb;

	return 0;
}
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电器与开关

#include <iostream>
using namespace std;

#define SAFE_DELETE(p) {if(p){delete p; p = nullptr;}}

class IEquipment {
public:
	virtual ~IEquipment(){}
	virtual void PowerOn() = 0;
	virtual void PowerOff() = 0;
};
class Light :public IEquipment {
public:
	void PowerOn() {
		cout << "开灯" << endl;
	}
	void PowerOff() {
		cout << "关灯" << endl;
	}
};
class Fan :public IEquipment {
public:
	void PowerOn() {
		cout << "打开风扇" << endl;
	}
	void PowerOff() {
		cout << "关闭风扇" << endl;
	}
};

class ISwitch {
protected:
	IEquipment* m_pEquipment = nullptr;
public:
	ISwitch(IEquipment* equipment) {
		m_pEquipment = equipment;
	}
	virtual ~ISwitch(){}
	virtual void On() = 0;
	virtual void Off() = 0;
};
class PullChainSwitch :public ISwitch {
public:
	PullChainSwitch(IEquipment* equipment):ISwitch(equipment){}
	//用拉链式开关打开电器
	void On() {
		cout << "用拉链式开关打开电器" << endl;
		if (m_pEquipment != nullptr) {
			m_pEquipment->PowerOn();
		}
	}
	//用拉链式开关关闭电器
	void Off() {
		cout << "用拉链式开关关闭电器" << endl;
		if (m_pEquipment != nullptr) {
			m_pEquipment->PowerOff();
		}
	}
};
class TwoPositionSwitch :public ISwitch {
public:
	TwoPositionSwitch(IEquipment* equipment) :ISwitch(equipment) {}
	//用两位开关打开电器
	void On() {
		cout << "用两位开关打开电器" << endl;
		if (m_pEquipment != nullptr) {
			m_pEquipment->PowerOn();
		}
	}
	//用两位开关关闭电器
	void Off() {
		cout << "用两位开关关闭电器" << endl;
		if (m_pEquipment != nullptr) {
			m_pEquipment->PowerOff();
		}
	}
};

int main() {
	IEquipment* light = new Light();
	IEquipment* fan = new Fan();

	ISwitch* pullChain = new PullChainSwitch(light);
	ISwitch* twoPosition = new TwoPositionSwitch(fan);

	pullChain->On();
	pullChain->Off();

	twoPosition->On();
	twoPosition->Off();
	
	SAFE_DELETE(twoPosition);
	SAFE_DELETE(pullChain);
	SAFE_DELETE(fan);
	SAFE_DELETE(light);

	return 0;
}
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