Strategy (C++实现）

// Strategy.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>

using namespace std;

class Strategy;

class Context
{
public:
 Context(Strategy *pStrategy=NULL):m_pStrategy(pStrategy)
 {
 }
 ~Context()
 {
 }

 void ContextInterface();
 void setStrategy(Strategy* s)
 {
  m_pStrategy=s;
 }
 
private:
 Strategy* m_pStrategy;
};

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

 virtual void AlgorithmInterface() = 0;
};

class ConcreateStrategyA
 : public Strategy
{
public:
 virtual ~ConcreateStrategyA(){}

 virtual void AlgorithmInterface()
 {
  cout << "AlgorithmInterface Implemented by ConcreateStrategyA/n";
 }
};

class ConcreateStrategyB
 : public Strategy
{
public:
 virtual ~ConcreateStrategyB(){}

 virtual void AlgorithmInterface()
 {
  cout << "AlgorithmInterface Implemented by ConcreateStrategyB/n";
 }
};

void Context::ContextInterface()
{
 if (NULL != m_pStrategy)
 {
  m_pStrategy->AlgorithmInterface();
 }
}

int _tmain(int argc, _TCHAR* argv[])
{
 Strategy* pStrategyA = new ConcreateStrategyA();
 Context*  pContext  = new Context(pStrategyA);
 pContext->ContextInterface();

 cout<<"========================"<<endl;

 Strategy* pStrategyB = new ConcreateStrategyB();
 pContext->setStrategy(pStrategyB);
 pContext->ContextInterface();

 delete pStrategyA;
 delete pStrategyB;
 delete pContext;

 return 0;
}