1,设计模式C++学习笔记之一(Strategy策略模式)
因为最近在学习设计模式,网上有些人介绍的设计模式发现还是不好容易理解。所以找到了这个博客中的设计模式发现还是很容易学习和理解的。http://www.cnblogs.com/wanggary/archive/2011/04/07/2008796.html
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 << "----------刚刚到吴国的时候拆第一个----------" << endl;
pContext = new CContext(new CBackDoor());
pContext->Operate();
delete pContext;
cout << "----------刘备乐不思蜀了,拆第二个了----------" << endl;
pContext = new CContext(new CGivenGreenLight());
pContext->Operate();
delete pContext;
cout << "----------孙权的小兵追了,咋办?拆第三个----------" << endl;
pContext = new CContext(new CBlockEnemy());
pContext->Operate();
delete pContext;
return 0;
}
这运行上述代码的过程中发现:error LNK2019: 无法解析的外部符号 "public: __thiscall IStrategy::IStrategy(void)" (??0IStrategy@@QAE@XZ),该符号在函数 "public: __thiscall CBackDoor::CBackDoor(void)" (??0CBackDoor@@QAE@XZ) 中被引用
编译器有报这个错误。我的开发环境是VS2010。查找网上可知:IStrategy.h中的纯虚函数的构造和析构函数没有函数体导致的