DesignPattern-Strategy

策略模式

 

策略模式定义：

    策略模式定义了算法（行为）簇分别封装起来，让他们之间可以相互替换，此模式让算法的变化独立于使用算法的客户。

 

1.找出应用中可能需要变化之处，把它们独立出来，不要和那些不需要变化的代码混在一起。
2.针对接口编程，而不是针对实现编程。
3.多用组合，少用继承。

 

Class Diagram:

Duck(鸭子）的行为Fly（飞）和 行为Quack(叫）抽象出来FlyBehavior和QuackBehavior。

DUCK.h

#if !defined(_DUCK_H)
#define _DUCK_H
#include "FlyBehavior.h"
#include "QuackBehavior.h"
#include "FlyNoWay.h"
#include "SmallQuack.h"

class Duck
{
public:
    Duck();
    ~Duck();

    void swim();

    virtual void display();
    void setQuackBehavior(QuackBehavior* quack);
    void setFlyBehavior(FlyBehavior* fly);
protected:
    void performQuack();
    void performFly();

protected:
    FlyBehavior* _flyBehavior;
    QuackBehavior* _quackBehavior;
};

#endif //_DUCK_H

FlyBehavior.h

#if !defined(_FLYBEHAVIOR_H)
#define _FLYBEHAVIOR_H


class FlyBehavior
{
public:
    virtual void fly() = 0;
};

#endif //_FLYBEHAVIOR_H

QuackBehavior.h

#if !defined(_QUACKBEHAVIOR_H)
#define _QUACKBEHAVIOR_H


class QuackBehavior
{
public:
    virtual void quack() =0;
};

#endif //_QUACKBEHAVIOR_H

FlyNoWay.h

#if !defined(_FLYNOWAY_H)
#define _FLYNOWAY_H

#include "FlyBehavior.h"

class FlyNoWay : public FlyBehavior
{
public:
    void fly();
};

#endif //_FLYNOWAY_H

FlyWithWing.h

#if !defined(_FLYWITHWING_H)
#define _FLYWITHWING_H

#include "FlyBehavior.h"

class FlyWithWing : public FlyBehavior
{
public:
    void fly();
};

#endif //_FLYWITHWING_H

SmallQuack.h

#if !defined(_SMALLQUACK_H)
#define _SMALLQUACK_H

#include "QuackBehavior.h"

class SmallQuack : public QuackBehavior
{
public:
    void quack();
};

#endif //_SMALLQUACK_H

Squake.h

#if !defined(_SQUEAK_H)
#define _SQUEAK_H

#include "QuackBehavior.h"

class Squeak : public QuackBehavior
{
public:
    void quack();
};

#endif //_SQUEAK_H

MallardDuck.h

#if !defined(_MALLARDDUCK_H)
#define _MALLARDDUCK_H

#include "Duck.h"

class MallardDuck : public Duck
{
public:
    MallardDuck();
    ~MallardDuck();
    //virtual void display();
};

#endif //_MALLARDDUCK_H

RedHeadDuck.h

#if !defined(_REDHEADDUCK_H)
#define _REDHEADDUCK_H

#include "Duck.h"

class RedHeadDuck : public Duck
{
public:
    RedHeadDuck();
    ~RedHeadDuck();
    //virtual void display();
};

#endif //_REDHEADDUCK_H

测试程序Strategy.cpp

#include "stdafx.h"
#include "Duck.h"
#include "MallardDuck.h"
#include "RedHeadDuck.h"
#include "FlyWithWing.h"
#include "Squeak.h"
#include "MuteQuack.h"
int main(int argc, char* argv[])
{
    printf("Hello World!\n");

    Duck *duck1 = new Duck();
    duck1->display();

    Duck* duck2 = new RedHeadDuck();
    duck2->setFlyBehavior(new FlyWithWing() );
    duck2->setQuackBehavior(new Squeak());
    duck2->display();


    Duck* duck3 = new MallardDuck();
    duck3->setQuackBehavior(new MuteQuack());
    duck3->display();
    return 0;
}

输出：

Hello World!
I cannot fly.
SmallQuack quack!
I can fly with my wing.
Squeak quack!
I cannot fly.
MuteQuack quack!
Press any key to continue

完整的工程代码，VC6.0项目。

 Strategy.rar