设计模式：适配器模式

适配器模式：将一个类的接口转换成客户希望的另一个接口，Adapter模式使得原本由于接口不兼容而不能一起工作的那些类可以一起工作

适配器模式有两种：

1.对象的适配器模式

2.类的适配器模式

 

适配器类图：

 

一个例子：

//IPromotion基类

#ifndef IPROMOTION_H #define IPROMOTION_H class IPromotion { public: IPromotion(){} virtual ~IPromotion(){} public: virtual double PromotionPrice()=0; }; #endif

 

//ComputerBook

//IPromotin.h #pragma once #include "IPromotin.h" class ComputerBook : public IPromotion { public: ComputerBook(double price=0.0); ~ComputerBook(void); public: virtual double PromotionPrice(); private: double bookprice; }; //IPromotin.cpp #include "ComputerBook.h" ComputerBook::ComputerBook(double price) { bookprice=price; } ComputerBook::~ComputerBook(void) { } double ComputerBook::PromotionPrice() { return bookprice*0.8; }

 

//IProxy基类

#ifndef IPROXY_H #define IPROXY_H class IProxy { public: IProxy(){} virtual ~IProxy(){} public: virtual double ProxyPrice()=0; }; #endif

 

//BookProxy

//IProxy.h #pragma once #include "IProxy.h" class BookProxy : public IProxy { public: BookProxy(double price=0.0); ~BookProxy(void); public: virtual double ProxyPrice(); private: double bookprice; }; //IProxy.cpp #include "BookProxy.h" BookProxy::BookProxy(double price) { bookprice=price; } BookProxy::~BookProxy(void) { } double BookProxy::ProxyPrice() { return bookprice*0.8; }

 

//对象适配器模式

//AdapterPriceObject.h #pragma once #include "IPromotin.h" class IProxy; class AdapterPriceObject : public IPromotion { public: AdapterPriceObject(IProxy* pro=0); ~AdapterPriceObject(void); public: void SetProxy(IProxy* pro); virtual double PromotionPrice(); private: IProxy* proxy; }; //AdapterPriceObject.cpp #include "AdapterPriceObject.h" #include "IProxy.h" AdapterPriceObject::AdapterPriceObject(IProxy* pro) { proxy=pro; } AdapterPriceObject::~AdapterPriceObject(void) { if(proxy) delete proxy; } void AdapterPriceObject::SetProxy(IProxy* pro) { if(proxy) delete proxy; proxy=pro; } double AdapterPriceObject::PromotionPrice() { return proxy->ProxyPrice (); }

 

//对象适配器模式

//AdapterPriceObject2.h #pragma once #include "IPromotin.h" #include "BookProxy.h" class AdapterPriceObject2 : public IPromotion,public BookProxy { public: AdapterPriceObject2(double pri=0.0); ~AdapterPriceObject2(void); public: virtual double PromotionPrice(); }; //AdapterPriceObject2.cpp #include "AdapterPriceObject2.h" AdapterPriceObject2::AdapterPriceObject2(double pri):BookProxy(pri) { } AdapterPriceObject2::~AdapterPriceObject2(void) { } double AdapterPriceObject2::PromotionPrice() { return BookProxy::ProxyPrice(); }

 

//主程序

#include "BookProxy.h" #include "ComputerBook.h" #include "AdapterPriceObject.h" #include "AdapterPriceObject2.h" #include <iostream> using std::cout; using std::endl; int main() { IPromotion* promotion=new AdapterPriceObject(new BookProxy(100)); cout<<"Price:"<<promotion->PromotionPrice ()<<endl; delete promotion; IPromotion* promotion2=new AdapterPriceObject2(150.0); cout<<"Price:"<<promotion2->PromotionPrice ()<<endl; delete promotion2; return 0; }

 

适配器的应用范围：

1.系统需要使用现有的类，而此类的接口不符合系统的需要

2.想要建立一个可以重复使用的类，用于与一些彼此之间没有太大关联的一些类，包括一些可能在将来引进的类一起工作。这些源类不一定有很复杂的接口。

3.（对对象适配器而言）在设计里，需要改变多个已有子类的接口，如果使用类的适配器模式，就要针对每一个子类做一个适配器，而这不太实际。