代理模式

简介

代理模式提供了一个代理，达到控制访问对象的目的。代理模式分为远程代理，保护代理，虚拟代理，缓冲代理和智能引用代理等。

UML 类图

示例

有句广告词，没有中间商赚差价，这个中间商很多时候就是代理的角色。中间商越多就是层层代理。很多商品都有一级代理商二级代理商等。在这里我们举一个火车票代售点的故事。
代理实现，proxy.h

#ifndef PROXY_H
#define PROXY_H
#include <iostream>
using namespace std;

#define SAFE_DELETE(p) if(p){delete (p); (p) = NULL;}
class CTicketSale
{
public:
    virtual void GetTicket() = 0;};

class CStationSale:public CTicketSale
{
public:
    void GetTicket()
    {cout<<"Get Ticket."<<endl;}
};

class CProxySale:public CTicketSale
{
public:
    CProxySale()
    {m_pTicketSale = new CStationSale;}
    ~CProxySale()
    {SAFE_DELETE(m_pTicketSale);
    }
    void GetTicket()
    {
        cout<<"Enter proxy:"<<endl;
        m_pTicketSale->GetTicket();}
private:
    CTicketSale* m_pTicketSale;
};

#endif

客户端调用，main.cpp

#include "proxy.h"

int main(int argc, char* argv[])
{
    CTicketSale* pProxySale = new CProxySale;
    pProxySale->GetTicket();
    SAFE_DELETE(pProxySale)
    return 0;
}