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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_
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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();
}
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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;
}
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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;
}
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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。
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