C++设计模式编程中proxy代理模式的使用实例

代理模式典型的结构图为：

实际上，代理模式的想法非常简单。

代理模式的实现：

完整代码示例（code）：代理模式的实现很简单，这里为了方便初学者的学习和参考，将给出完整的实现代码（所有代码采用 C++实现，并在 VC 6.0 下测试运行）。

代码片断 1：Proxy.h

//Proxy.h
#ifndef _PROXY_H_
#define _PROXY_H_
class Subject{
  public:
  virtual ~Subject();
  virtual void Request() = 0;
  protected:
  Subject();
  private:
};
class ConcreteSubject:public Subject{
  public:
  ConcreteSubject();
  ~ConcreteSubject();
  void Request();
  protected:
  private:
};
class Proxy{
  public:
  Proxy();
  Proxy(Subject* sub);
  ~Proxy();
  void Request();
  protected:
  private:
  Subject* _sub;
};
#endif //~_PROXY_H_

代码片断 2：Proxy.cpp

//Proxy.cpp
#include "Proxy.h"
#include <iostream>
using namespace std;
Subject::Subject(){
}
Subject::~Subject(){
}
ConcreteSubject::ConcreteSubject(){
}
ConcreteSubject::~ConcreteSubject(){
}
void ConcreteSubject::Request(){
  cout<<"ConcreteSubject......request
  ...."<<endl;
}
Proxy::Proxy(){
}
Proxy::Proxy(Subject* sub){
  _sub = sub;
}
Proxy::~Proxy(){
  delete _sub;
}
void Proxy::Request(){
  cout<<"Proxy request...."<<endl;
  _sub->Request();
}

代码片断 3：main.cpp

//main.cpp
#include "Proxy.h"
#include <iostream>
using namespace std;
int main(int argc,char* argv[]){
   Subject* sub = new ConcreteSubject();
  Proxy* p = new Proxy(sub);
  p->Request();
  return 0;
}

代码说明：代理模式的实现很简单，这里不做多余解释。可以看到，示例代码运行后，p 的 Request 请求实际上是交给了 sub 来实际执行。

再来看一个例子：

#include <iostream>
#include <string>
using namespace std; 

class Receiver
{
private:
  string name; 

public:
  Receiver(string name):name(name)
  { 

  }
  string GetName()
  {
    return name;
  }
}; 

class Subject
{
public:
  virtual void display(){}
}; 

class Sender:public Subject
{
  Receiver *someone;
public:
  void SetReceiver(Receiver *someone)
  {
    this->someone = someone;
  }
  virtual void display()
  {
    cout<<"i hate you:" << someone->GetName()<<endl;
  }
}; 

class Proxy:public Subject
{
public:
  Subject *realobject; 

  void SetClient(Subject *client)
  {
    this->realobject = client;
  } 

  void display()
  {
    realobject->display();
  }
}; 

int main()
{
  Receiver *recv = new Receiver("nobody");
  Sender *obj  = new Sender;
  obj->SetReceiver(recv);
  Proxy *proxy = new Proxy;
  proxy->SetClient(obj); 

  proxy->display(); 

  system("pause");
  return 0;
}

由此可见，代理模式最大的好处就是实现了逻辑和实现的彻底解耦。