二、策略模式

//Strategy.h
#ifndef _STRATEGY_H
#define _STRATEGY_H
class Strategy
{
public:
	Strategy();
	virtual ~Strategy();
	virtual void AlgorithmInterface()=0;
};
class ConcreteStrategyA :public Strategy
{
public:
	ConcreteStrategyA();
	virtual ~ConcreteStrategyA();
	void AlgorithmInterface();
};
class ConcreteStrategyB :public Strategy
{
public:
	ConcreteStrategyB();
	virtual ~ConcreteStrategyB();
	void AlgorithmInterface();
};
#endif

//Strategy.cpp
#include "Strategy.h"
#include <iostream>
using namespace std;
Strategy::Strategy()
{

}
Strategy::~Strategy()
{
	cout<<"~Strategy……"<<endl;
}
void Strategy::AlgorithmInterface()
{

}
ConcreteStrategyA::ConcreteStrategyA()
{

}
ConcreteStrategyA::~ConcreteStrategyA()
{
	cout<<"~ConcreteStrategyA……"<<endl;
}
void ConcreteStrategyA::AlgorithmInterface()
{
	cout<<"Algorithm of StrategyA"<<endl;
}
ConcreteStrategyB::ConcreteStrategyB()
{

}
ConcreteStrategyB::~ConcreteStrategyB()
{
	cout<<"~ConcreteStrategyB……"<<endl;
}
void ConcreteStrategyB::AlgorithmInterface()
{
	cout<<"Algorithm of StrategyB"<<endl;
}

//Context.h
#ifndef _CONTEXT_H
#define _CONTEXT_H
class Strategy;
class Context
{
public:
	Strategy* pStrategy;
	Context(Strategy* stg);
	virtual ~Context();
	virtual void DoAction();
};
#endif

//Context.cpp
#include "Context.h"
#include "Strategy.h"
Context::Context(Strategy* stg)
{
	pStrategy = stg;
}

Context::~Context()
{
	if (!pStrategy)
	{
		delete pStrategy;
	}
}
void Context::DoAction()
{
	pStrategy->AlgorithmInterface();
}

//main.cpp
#include "Context.h"
#include "Strategy.h"
#include <iostream>


int main()
{
	Context *ct = NULL;
	Strategy* st = new ConcreteStrategyA();
	ct = new Context(st);
	ct->DoAction();
	
	st = new ConcreteStrategyB();
	ct = new Context(st);
	ct->DoAction();
	return 0;
}