设计模式C++（Strategy策略模式）

转载：http://blog.csdn.net/jeje1115/article/details/7069934

1.1.解释

main()，赵云

CContext，锦囊

IStrategy，策略接口

CBackDoor，策略之一

CGivenGreenLight，策略之二

CBlockEnemy，策略之三

说明：一个策略放到一个锦囊里。当用的时候，找到这个锦囊，从锦囊里拿出策略来使用。

注意：锦囊只是简单的装载和调用策略，锦囊里没有逻辑。策略会有更大的自主权，运行更多的逻辑。

看代码：

//Context.h

#pragma once
#include "IStrategy.h"
class CContext
{
public:
    CContext(IStrategy *pStrategy);
    ~CContext(void);
    void Operate(void);
private:
    IStrategy *m_pStrategy;
};

//Context.cpp

#include "StdAfx.h"
#include "Context.h"
CContext::CContext(IStrategy *pStrategy)
{
    this->m_pStrategy = pStrategy;
}
CContext::~CContext(void)
{
    delete this->m_pStrategy;
}
void CContext::Operate(void)
{
    this->m_pStrategy->Operate();
}

//IStrategy.h

#pragma once

class IStrategy
{
public:
    IStrategy(void);
    virtual ~IStrategy(void);
    virtual void Operate(void) = 0;
};

//BackDoor.h

#pragma once
#include "istrategy.h"
class CBackDoor :
    public IStrategy
{
public:
    CBackDoor(void);
    ~CBackDoor(void);
    void Operate(void);
};

//BackDoor.cpp

#include "StdAfx.h"
#include "BackDoor.h"
#include <iostream>
using std::cout;
using std::endl;
CBackDoor::CBackDoor(void)
{
}
CBackDoor::~CBackDoor(void)
{
}
void CBackDoor::Operate(void)
{
cout << "找乔国老帮忙，让吴国太给孙权施加压力" << endl;
}

//GivenGreenLight.h

#pragma once
#include "istrategy.h"
class CGivenGreenLight :
    public IStrategy
{
public:
    CGivenGreenLight(void);
    ~CGivenGreenLight(void);
    void Operate(void);
};

//GivenGreenList.cpp

#include "StdAfx.h"
#include "GivenGreenLight.h"
#include <iostream>
using std::cout;
using std::endl;
CGivenGreenLight::CGivenGreenLight(void)
{
}
CGivenGreenLight::~CGivenGreenLight(void)
{
}
void CGivenGreenLight::Operate(void)
{
cout << "求吴国太开个绿灯，放行！" << endl;
}

//BlockEnemy.h

#pragma once
#include "istrategy.h"
class CBlockEnemy :
    public IStrategy
{
public:
    CBlockEnemy(void);
    ~CBlockEnemy(void);
    void Operate(void);
};

//BlockEnemy.cpp

#include "StdAfx.h"
#include "BlockEnemy.h"
#include <iostream>
using std::cout;
using std::endl;
CBlockEnemy::CBlockEnemy(void)
{
}
CBlockEnemy::~CBlockEnemy(void)
{
}
void CBlockEnemy::Operate()
{
cout << "孙夫人断后，挡住追兵" << endl;
}

//Strategy.cpp

#include "stdafx.h"
#include "Context.h"
#include "BackDoor.h"
#include "GivenGreenLight.h"
#include "BlockEnemy.h"
#include <iostream>
using std::cout;
using std::endl;
int _tmain(int argc, _TCHAR* argv[])
{
CContext *pContext;

cout << "\14\n\n\n\n\17" << endl;
    cout << "----------刚刚到吴国的时候拆第一个----------" << endl;
    pContext = new CContext(new CBackDoor());
    pContext->Operate();
    delete pContext;

cout << "\14\n\n\n\n\17" << endl;
    cout << "----------刘备乐不思蜀了，拆第二个了----------" << endl;
    pContext = new CContext(new CGivenGreenLight());
    pContext->Operate();
    delete pContext;

cout << "\14\n\n\n\n\17" << endl;
    cout << "----------孙权的小兵追了，咋办？拆第三个----------" << endl;
    pContext = new CContext(new CBlockEnemy());
    pContext->Operate();
    delete pContext;

_CrtSetDbgFlag(_CRTDBG_LEAK_CHECK_DF | _CRTDBG_ALLOC_MEM_DF);
_CrtDumpMemoryLeaks();
return 0;
}

一个锦囊只能装一个妙计，赵云可以有多个锦囊。属于对象行为型模式。很简单的一个模式了，貌似这24个里面，这是最简单的了。也好，先用一个简单容易的开头，都说万事开头难，找个简单的开始，鼓励自己坚持学下来，就会有收获。博客也会起到这个作用吧，鼓励自己。上图不是单纯的抽象出来的模式类图，而只是描述了代码里用到的类之间的关系图。真正的抽象类图，只有策略接口和一个策略实现类，还有CContext类以及Client。