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。
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