Proxy 代理模式

关键，代理起到站位作用，等到真正用的时候再真正的去实例化真正的类

#include <cstdlib>
#include <iostream>

using namespace std;

class Subject
{
public:
  virtual ~Subject(){cout<<"析构Subject基类"<<endl;}
  virtual void Do() = 0;
};
class RealSubject:public Subject
{
public:
  ~RealSubject(){cout<<"析构RealSubject子类"<<endl;}
  virtual void Do(){cout<<"RealSubject do sth."<<endl;}
};
class Proxy:public Subject
{
  Subject* m_pSub;
public:
  Proxy():m_pSub(NULL){}
  ~Proxy()
  {
    cout<<"构Proxy子类"<<endl;
    if(m_pSub != NULL)delete m_pSub;
  }
  virtual void Do()
  {
    if(m_pSub == NULL){m_pSub = new RealSubject;}
    m_pSub->Do();
  }
};
void foo(Subject* pSub)
{
  pSub->Do();
}
int main(int argc, char *argv[])
{
    Subject* pSub = new Proxy;
    foo(pSub);
    delete pSub;
    system("PAUSE");
    return EXIT_SUCCESS;
}