C++设计模式 代理模式

最近在看《大话设计模式》这本书，看到了代理模式这一章，正好有时间，简单的写一下自己的理解。

代理模式就是其实就是对 真实的实体做了一层封装，客户端调用的时候 直接访问代理类，代理类再根据实际情况去操作真实的实体。在操作实体之前，代理类可以做一些判定或者其他的操作，这就是代理类存在的意义。一般代理类中都会保存一个 实体类的对象的引用或者指针。

代理类和实体类具有相同的接口，一般情况下他们继承自一个接口类。

1.UML图：

2.代码：

Proxy.h

#ifndef PROXY_H_#define PROXY_H_#include <stdio.h>#include <stdlib.h>#include <string>#include <string.h>using std::string;class Subject{public:Subject() {};virtual ~Subject() {};virtual void Request() = 0;};//实体类class RealSubject :public Subject{public:RealSubject();RealSubject(string &strName);~RealSubject();void Request();private:string m_strName;};//代理类class Proxy :public Subject{public:Proxy();~Proxy();void SetSubject(RealSubject *pRealSubject);//设置内部实体对象void Request();private:RealSubject *m_pRealSubject;//代理类内部的实体类引用};#endif

proxy.cpp:

#include "Proxy.h"RealSubject::RealSubject(){}RealSubject::RealSubject(string &strName){m_strName = strName;}RealSubject::~RealSubject(){}void RealSubject::Request(){printf("RealSuject Name : %s\n", m_strName.c_str());}Proxy::Proxy(){m_pRealSubject = NULL;}Proxy::~Proxy(){if (m_pRealSubject){delete m_pRealSubject;m_pRealSubject = NULL;}}void Proxy::SetSubject(RealSubject *pRealSubject){if (m_pRealSubject){delete m_pRealSubject;m_pRealSubject = NULL;}m_pRealSubject = pRealSubject;}void Proxy::Request(){if (NULL == m_pRealSubject){string strName = "RealSubject";m_pRealSubject = new RealSubject(strName);}//做一些代理需要做的事情printf("Proxy do something\n");m_pRealSubject->Request();}

Test.cpp:

#include "Proxy.h"int main(){//1Proxy *pProxy = new Proxy();pProxy->Request();delete pProxy;pProxy = NULL;//2string strName = "MyRealSubject";RealSubject *pRealSubject = new RealSubject(strName);pProxy = new Proxy();pProxy->SetSubject(pRealSubject);pProxy->Request();delete pProxy;pProxy = NULL;return 0;}