设计模式--代理模式（Proxy）-优快云博客

本文通过租房的例子介绍了代理模式的基本概念及其实现方式，包括普通代理和强制代理两种形式，并探讨了代理模式的优点及其应用场景。

Proxy

一个很简单的例子，房东要出租房子

一般模式：

class CHouseOwner { public: CHouseOwner(CString strHouseAddress, CString strTeleNum, CString strName); void SetPrice(int iPrice){//dosomething} void Advertising(){//dosomething} void TakeToSeeTheHouse(CHouseFinder houseFinder){//dosomething} void TakeAgreeMent(){//dosomething} } class CHouseFinder { public: CHouseFinder(CString strTeleNum, CString strName); void BrowseAdvertising(CString& strName, CString& telNum); void ContactWithHouseOwner(CString strName, CString strTeleNum); void SeeTheHouse(CHouseOwner houseOwner); void TakeAgreeMent(); } void main() { CHouseOwner houseOwner("西二旗XX楼XX户"，"123456789", "小张"); houseOwner.SetPrice(2000); houseOwner.Advertising(); CHouseFinder houseFinder("111111111", "小王"); CString strName,strTel; houseFinder.BrowseAdvertising(strName,strTel); houseFinder.ContactWithHouseOwner(strName,strTel); houseOwner.TakeToSeeTheHouse(houseFinder); houseFinder.SeeTheHouse(houseOwner); houseOwner.TakeAgreeMent(); houseFinder.TakeAgreeMent(); }

代理模式：中介机构出现以后，中介的职能之一就是作为房东出租房子的代理，对于只想收房租而不愿意做那些带人看房子之类的事的房东可以委托给中介机构代理：
类图：

普通代理：

父类： class CIHouseOwner { public: void SetPrice(int iPrice){} void Advertising(){} void TakeToSeeTheHouse(CHouseFinder houseFinder){} void TakeAgreeMent(){} } class CHouseProxy public CIHouseOwner { public: CHouseProxy(CString strHouseAddress, CString strTeleNum, CString strName) { CHouseOwner* phouseOwner = new(strHouseAddress，strTeleNum, strName); } void SetPrice(int iPrice){phouseOwner->SetPrice(iPrice)} void Advertising(){//dosomething} void TakeToSeeTheHouse(CHouseFinder houseFinder){//dosomething} void TakeAgreeMent(){phouseOwner->TakeAgreeMent()} } void main() { CHouseProxy houseProxy("西二旗XX楼XX户"，"123456789", "小张"); houseProxy.SetPrice(2000); houseProxy.Advertising(); CHouseFinder houseFinder("111111111", "小王"); CString strName,strTel; houseFinder.BrowseAdvertising(strName,strTel); houseFinder.ContactWithHouseOwner(strName,strTel); houseProxy.TakeToSeeTheHouse(houseFinder); houseFinder.SeeTheHouse(houseProxy); houseProxy.TakeAgreeMent(); houseFinder.TakeAgreeMent

在该模式下，调用者（houseFinder）只知代理而不用知道真实的角色是谁，屏蔽了真实角色的变更对高层模块的影响，真实的主题角色想怎么修改就怎么修改，对高层次的模块没有任何影响，只要你实现了接口所对应的方法，该模式非常适合对扩展性要求较高的场合。在实际的项目中，一般都是通过约定来禁止new一个真实的角色。

强制代理：

父类： class CIHouseOwner { public: void SetPrice(int iPrice){} void Advertising(){} void TakeToSeeTheHouse(CHouseFinder houseFinder){} void TakeAgreeMent(){} } class CHouseProxy public CIHouseOwner { public: CHouseProxy(CIHouseOwner* phouseOwner) { m_phouseOwner = phouseOwner; } void SetPrice(int iPrice){m_phouseOwner->SetPrice(iPrice)} void Advertising(){//dosomething} void TakeToSeeTheHouse(CHouseFinder houseFinder){//dosomething} void TakeAgreeMent(){m_phouseOwner->TakeAgreeMent()} } class CHouseOwner public CIHouseOwner { public: CHouseOwner(CString strHouseAddress, CString strTeleNum, CString strName); void SetPrice(int iPrice) { if(IsProxy()) { //dosomething } else { return; } } void TakeAgreeMent() { if(IsProxy()) { //dosomething } else { return; } } CHouseProxy* GetProxy() {CHouseProxy* pPorxy = new CHouseProxy(this); return pPorxy; } private: IsProxy(){//doSomething} } void main() { CHouseOwner houseOwner("西二旗XX楼XX户"，"123456789", "小张"); CHouseProxy* pHouseProxy = houseOwner.GetProxy(); houseProxy.SetPrice(2000); houseProxy.Advertising(); CHouseFinder houseFinder("111111111", "小王"); CString strName,strTel; houseFinder.BrowseAdvertising(strName,strTel); houseFinder.ContactWithHouseOwner(strName,strTel); houseProxy.TakeToSeeTheHouse(houseFinder); houseFinder.SeeTheHouse(houseProxy); houseProxy.TakeAgreeMent(); houseFinder.TakeAgreeMent(); }

强制代理的概念就是要从真实角色查找到代理角色，不允许直接访问真实角色。高层模块只要调用getProxy就可以访问真实角色的所有方法，它根本就不需要产生一个代理出来，代理的管理已经由真实角色自己完成。

代理模式定义

代理模式（Proxy Pattern）是一个使用率非常高的模式，定义如下：为其他对象提供一种代理以控制对这个对象的访问。

Subject抽象主题角色：抽象主题类可以是抽象类也可以是接口，是一个最普通的业务类型定义，无特殊要求。
RealSubject具体主题角色：也叫被委托角色、被代理角色。它是业务逻辑的具体执行者。
Proxy代理主题角色：也叫委托类、代理类。它负责对真实角色的应用，把所有抽象主题类定义的方法限制委托给真实主题角色实现，并且在真实主题角色处理完毕前后做预处理和善后处理工作。

代理的另一种扩展

代理类不仅仅可以实现主题接口，也可以实现其他接口完成不同的任务。如：

Class CProxy { public: void Count();//收费 } class CHouseProxy public CIHouseOwner，public CProxy { public: CHouseProxy(CIHouseOwner* phouseOwner) { m_phouseOwner = phouseOwner; } void SetPrice(int iPrice){m_phouseOwner->SetPrice(iPrice)} void Advertising(){//dosomething} void TakeToSeeTheHouse(CHouseFinder houseFinder){//dosomething} void TakeAgreeMent(){m_phouseOwner->TakeAgreeMent()} void Count(){//dosomething} }