作用:
定义一系列的算法,把它们一个个封装起来, 并且使它们可相互替换.本模式使得算法可独立于使用它的客户而变化.
解析:
简而言之一句话,Strategy模式是对算法的封装.处理一个问题的时候可能有多种算法,这些算法的接口(输入参数,输出参数等)都是一致的,那么可以考虑采用Strategy模式对这些算法进行封装,在基类中定义一个函数接口就可以了.
实现:
1)Strategy.h
/**//********************************************************************
created: 2006/08/06
filename: Strategy.h
author: 李创
http://www.cppblog.com/converse/
purpose: Strategy模式的演示代码
*********************************************************************/
#ifndef STRATEGY_H
#define STRATEGY_H
class Strategy;
class Context
{
public:
Context(Strategy *pStrategy);
~Context();
void ContextInterface();
private:
Strategy* m_pStrategy;
};
class Strategy
{
public:
virtual ~Strategy(){}
virtual void AlgorithmInterface() = 0;
};
class ConcreateStrategyA
: public Strategy
{
public:
virtual ~ConcreateStrategyA(){}
virtual void AlgorithmInterface();
};
#endif
2)Strategy.cpp
/**//********************************************************************
created: 2006/08/06
filename: Strategy.cpp
author: 李创
http://www.cppblog.com/converse/
purpose: Strategy模式的演示代码
*********************************************************************/
#include <iostream>
#include "Strategy.h"
Context::Context(Strategy *pStrategy)
: m_pStrategy(pStrategy)
{
}
Context::~Context()
{
delete m_pStrategy;
m_pStrategy = NULL;
}
void Context::ContextInterface()
{
if (NULL != m_pStrategy)
{
m_pStrategy->AlgorithmInterface();
}
}
void ConcreateStrategyA::AlgorithmInterface()
{
std::cout << "AlgorithmInterface Implemented by ConcreateStrategyA\n";
}
3)Main.cpp
/**//********************************************************************
created: 2006/08/06
filename: Main.cpp
author: 李创
http://www.cppblog.com/converse/
purpose: Strategy模式的测试代码
*********************************************************************/
#include "Strategy.h"
int main()
{
Strategy* pStrategy = new ConcreateStrategyA();
Context* pContext = new Context(pStrategy);
pContext->ContextInterface();
delete pContext;
return 0;
}