c++设计模式(10)-Strategy模式

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.

UML结构图:



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

/**//********************************************************************
filename: Strategy.h
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

/**//********************************************************************
filename: Strategy.cpp
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

/**//********************************************************************
filename: Main.cpp
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;
}