：策略模式--Duck

原则：封装变化的部分；针对超类编程，不针对实现；多组合少继承；

#ifndef __DUCK_H__
#define __DUCK_H__
#include "FlyBehavior.h"
#include "QuackBehavior.h"

class Duck
{
public:
	Duck()
	{

	}

	virtual ~Duck()
	{

	}

	virtual void performFly()
	{

	}

	virtual void performQuack()
	{

	}

	void setQuack(QuackBehavior *t)
	{
		if (t != NULL)
		{
			quackBehavior = t;
		}
	}

	void setFly(FlyBehavior *t)
	{
		if (t != NULL)
		{
			flyBehavior = t;
		}
	}

protected:
	QuackBehavior *quackBehavior;
	FlyBehavior   *flyBehavior;
};

class MuDuck :public Duck
{
public:
	MuDuck()
	{
		quackBehavior = new SqueakQuack();
		flyBehavior = new FlyWithWings();
	}

	virtual ~MuDuck()
	{
		delete quackBehavior;
		delete flyBehavior;
	}

	void performFly()
	{
		flyBehavior->fly();
	}

	void performQuack()
	{
		quackBehavior->quack();
	}

};
#endif

#ifndef __QUACKBEHAVIOR_H__
#define __QUACKBEHAVIOR_H__
#include <iostream>
using namespace std;

class QuackBehavior
{
public:
	QuackBehavior()
	{

	}

	virtual void quack() = 0
	{

	}
};

class MuteQuack : public QuackBehavior
{
public:
	MuteQuack()
	{

	}

	void quack()
	{
		cout << "Mute Quack" << endl;
	}
};

class SqueakQuack :public QuackBehavior
{
public:
	SqueakQuack()
	{

	}

	void quack()
	{
		cout << "Squeak Quack" << endl;
	}
};

#endif

#ifndef __FLYBEHAVIOR_H__
#define __FLYBEHAVIOR_H__
#include <iostream>
using namespace std;

class FlyBehavior
{
public:
	FlyBehavior()
	{

	}

	virtual void fly() = 0 {}
};

class FlyWithWings : public FlyBehavior
{
public:
	FlyWithWings(){}
	void fly()
	{
		cout << "fly? Yes,I Can!" << endl;
	}
};

class FlyNoWay : public FlyBehavior
{
public:
	FlyNoWay(){}
	void fly()
	{
		cout << "fly? No! " << endl;
	}
};

class FlyRocket :public FlyBehavior
{
public:
	FlyRocket()
	{

	}
	void fly()
	{
		cout << "fly? With Rocket" << endl;
	}

};

#endif

客户端代码

#include <iostream>
#include "Duck.h"
using namespace std;
int main()
{
	Duck *duck = new MuDuck();
	duck->performFly();
	duck->performQuack();

	duck->setFly(new FlyRocket());
	duck->performFly();

	delete duck;

	return 0;
}