Proxy 模式

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本文通过C++代码示例介绍了代理模式的基本概念及其实现方式。代理模式为真实对象提供了一个代理来控制对该对象的访问，可以用于延迟加载等场景。

作用:

为其他对象提供一种代理以控制对这个对象的访问

#include <iostream>
using namespace std;  

class Subject
{
public:
	Subject(){}
	virtual ~Subject(){}

	virtual void request() = 0;
private:
};

class RealSubject:public Subject
{
public:
	RealSubject(){
		cout << "Constructing a RealSubject\n";
	}
	~RealSubject(){

	}
	void request(){
		cout << "Request By RealSubject\n";
	}
};
class Proxy:public Subject
{
public:
	Proxy():realSubject(NULL){
		cout << "Constructing a Proxy\n";
	}
	~Proxy(){
		delete realSubject;
		realSubject = NULL;
	}
	void request(){
		if (NULL == realSubject)
		{
			cout << "Request By Proxy\n";
			realSubject = new RealSubject();
		}
		realSubject->request();
	}
private:
	RealSubject *realSubject;
};
int main(void)  
{   
	Subject* pProxy = new Proxy();
	pProxy->request();

	delete pProxy;

	return 0;  
}