前言

最近在学习《Headfirst设计模式》，里面的例子都是Java的。但是我对Java并不熟悉，所以试着用C++来实现书中的例子。

 

先来看看Duck以及子类

Duck.h

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

class Duck
{
private:
    FlyBehavior *m_p_fly_behavior;
public:
    virtual void quack() { std::cout << "--quack--" << std::endl; }
    virtual void swim() { std::cout << "--swim--" << std::endl; }
    virtual void display() { std::cout << "--duck--" << std::endl; }

    virtual void fly() { if ( m_p_fly_behavior) { m_p_fly_behavior->fly(); } };
    void set_fly_behavior( FlyBehavior *p_fly_behavior) { m_p_fly_behavior = p_fly_behavior; }

    Duck() : m_p_fly_behavior(NULL) {}
    virtual ~Duck() { if (m_p_fly_behavior) { delete m_p_fly_behavior; } }
};

 

MallardDuck.h

#include "Duck.h"
#include "FlyWithWings.h"

class MallardDuck : public Duck
{
public:
    void display() { std::cout << "--MallardDuck--" << std::endl; }
    MallardDuck() { set_fly_behavior( new FlyWithWings() ); }
};

 

RedheadDuck.h

#include "FlyWithWings.h"
class RedheadDuck : public Duck
{
public:
    void display() { std::cout << "--RedheadDuck--" << std::endl; }
    RedheadDuck() { set_fly_behavior( new FlyWithWings() ); }
};

 

RubberDuck.h

#include "FlyNoWay.h"

class RubberDuck : public Duck
{
public:
    void display() { std::cout << "--RubberDuck--" << std::endl; }
    void quack() { std::cout << "--squeak--" << std::endl; }
    RubberDuck() { set_fly_behavior( new FlyNoWay() ); }
};

 

再来看看FlyBehavior类及其子类

FlyBehavior.h

#include <iostream>

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

 

FlyWithWings.h

#include "FlyBehavior.h"

class FlyWithWings : public FlyBehavior
{
public:
    void fly () { std::cout << "--fly with wings--" << std::endl; }
};

 

FlyNoWay.h

#include "FlyBehavior.h"

class FlyNoWay : public FlyBehavior
{
public:
    void fly() { std::cout << "--can not fly--" << std::endl; }
};

 

最后是主函数

main.cpp

#include "MallardDuck.h"
#include "RedheadDuck.h"
#include "RubberDuck.h"
#include <vector>

void test()
{
    std::vector<Duck *> p_ducks;
    p_ducks.push_back( new MallardDuck() );
    p_ducks.push_back( new RedheadDuck() );
    p_ducks.push_back( new RubberDuck() );

    for (std::vector<Duck *>::iterator it = p_ducks.begin(); it < p_ducks.end(); it ++)
    {
        std::cout << std::endl;
        (*it)->display();
        (*it)->quack();
        (*it)->swim();
        (*it)->fly();
        delete (*it);
    }
}

int main()
{
    while (true)
    {
        test();
    }
}

 

稍作解释

main函数中死循环的调用test函数的意图是测试以上实现有没有内存泄露。