Bridge模式

Bridge模式

在面向对象的开发过程中，要做到2点：1.高内聚　2.松耦合．但是在实际开发过程中难以把握，例如会遇到这样的问题：

１）客户给了一个需求，之后我们用一个类A来实现．

２）客户的需求有了变化，要用到2个算法来实现．于是我们通过定义一个抽象基类A，再用两个具体类A1和A2实现这两个算法．

３）客户需求又有了变化，要求在2个操作系统上实现．我们再抽象一个层次，不同操作系统抽象为A0和A1，每个操作系统上有2个算法，实现为A00，A01和A10，A11，总共有4个类．

４）客户需求如果再有变化，那么我们又要重新设计．

Bridge(桥接)模式正是解决这个问题的．Bridge模式的核心在于将抽象部分和实现分离，它们两者可以独立地变化．

它的类结构图如下：

下面是实现的代码

//Abstraction.h

//Abstraction.h #ifndef _ABSTRACTION_H_ #define _ABSTRACTION_H_ class AbstractionImp; class Abstraction { public: virtual ~Abstraction(); virtual void Operation() = 0 ; protected: Abstraction(); }; class RefinedAbstraction :public Abstraction { public: RefinedAbstraction(AbstractionImp* imp); ~RefinedAbstraction(); void Operation() ; private: AbstractionImp* _imp; }; #endif

//Abstraction.cpp

#include"Abstraction.h" #include"AbstractionImp.h" Abstraction::Abstraction() { } Abstraction::~Abstraction() { } RefinedAbstraction::RefinedAbstraction(AbstractionImp* imp) { _imp = imp; } RefinedAbstraction::~RefinedAbstraction() { } void RefinedAbstraction::Operation() { _imp->Operation(); }

//AbstractionImp.h

//AbstractionImp.h #ifndef _ABSTRACTIONIMP_H_ #define _ABSTRACTIONIMP_H_ class AbstractionImp { public: virtual ~AbstractionImp(); virtual void Operation() = 0; protected: AbstractionImp(); }; class ConcreteAbstractionImpA :public AbstractionImp { public: ConcreteAbstractionImpA(); ~ConcreteAbstractionImpA(); virtual void Operation(); }; class ConcreteAbstractionImpB :public AbstractionImp { public: ConcreteAbstractionImpB(); ~ConcreteAbstractionImpB(); virtual void Operation(); }; #endif

//AbstractionImp.cpp

#include"AbstractionImp.h" #include<iostream> using namespace std; AbstractionImp::AbstractionImp() { } AbstractionImp::~AbstractionImp() { } ConcreteAbstractionImpA::ConcreteAbstractionImpA() { } ConcreteAbstractionImpA::~ConcreteAbstractionImpA() { } void ConcreteAbstractionImpA::Operation() { cout << "ConcreteAbstractionImpA Operation" << endl; } ConcreteAbstractionImpB::ConcreteAbstractionImpB() { } ConcreteAbstractionImpB::~ConcreteAbstractionImpB() { } void ConcreteAbstractionImpB::Operation() { cout << "ConcreteAbstractionImpB Operation" << endl; }

//main.cpp

#include"Abstraction.h" #include"AbstractionImp.h" int main() { AbstractionImp* impA = new ConcreteAbstractionImpA(); AbstractionImp* impB = new ConcreteAbstractionImpB(); Abstraction* absA = new RefinedAbstraction(impA); Abstraction* absB = new RefinedAbstraction(impB); absA->Operation(); absB->Operation(); return 0; }