Head First 设计模式 （三） 装饰者模式（decorator pattern） C++实现

装饰者模式动态地将责任附加到对象上。若要扩展功能，装饰者提供了比继承更有弹性的替代方式

设计原则：类应该对扩展开放，对修改关闭

类图：

 C++ 代码如下：

源码下载：http://download.csdn.net/detail/lingyunjinzhu/5184135

#ifndef BEVERAGE_H
#define BEVERAGE_H
#include

class Beverage
{
    public:
        Beverage();
        virtual ~Beverage();
        virtual std::string getDescription();
        virtual double cost(){ return 0;};
        std::string description;
    protected:
    private:
      // std::string description;
};

#endif // BEVERAGE_H

#include "Beverage.h"
#include 
Beverage::Beverage():description("Unknow name")
{
}
Beverage::~Beverage()
{

}
std::string Beverage::getDescription()
{
    return description;
}

#ifndef HOUSEBLEND_H
#define HOUSEBLEND_H

#include "Beverage.h"


class HouseBlend : public Beverage
{
    public:
        HouseBlend();
        ~HouseBlend();
        double cost();
    protected:
    private:
};

#endif // HOUSEBLEND_H

#include "HouseBlend.h"

HouseBlend::HouseBlend()
{
    description="House Blend Coffee";
}

HouseBlend::~HouseBlend()
{
    //dtor
}
double HouseBlend::cost()
{
    return 0.89;
}

#ifndef DARKROAST_H
#define DARKROAST_H

#include "Beverage.h"


class DarkRoast : public Beverage
{
    public:
        DarkRoast();
        ~DarkRoast();
        double cost();
    protected:
    private:
};

#endif // DARKROAST_H

#include "DarkRoast.h"
#include
using namespace std;
DarkRoast::DarkRoast()
{
    description= "DarkRoast";
}

DarkRoast::~DarkRoast()
{
    //dtor
}
double DarkRoast::cost()
{
    return 0.99;
}

#ifndef ESPRESSO_H
#define ESPRESSO_H

#include "Beverage.h"


class Espresso : public Beverage
{
    public:
        Espresso();
        ~Espresso();
        double cost();
    protected:
    private:
};

#endif // ESPRESSO_H

#include "Espresso.h"

Espresso::Espresso()
{
    description="Espresso";
}

Espresso::~Espresso()
{
    //dtor
}
double Espresso::cost()
{
    return 1.99;
}

#ifndef DECAT_H
#define DECAT_H

#include "Beverage.h"


class Decat : public Beverage
{
    public:
        Decat();
        ~Decat();
        double cost();
    protected:
    private:
};

#endif // DECAT_H
#include "Decat.h"

Decat::Decat()
{
    description="Decat";
}

Decat::~Decat()
{
    //dtor
}
double Decat::cost()
{
    return 1.05;
}

#ifndef CONDIMENTDECORATOR_H
#define CONDIMENTDECORATOR_H
#include"Beverage.h"

class CondimentDecorator: public Beverage
{
    public:
        CondimentDecorator();
        virtual ~CondimentDecorator();
        virtual std::string getDescription(){return "";};
    protected:
    private:
};

#endif // CONDIMENTDECORATOR_H

#include "CondimentDecorator.h"

CondimentDecorator::CondimentDecorator()
{
    //ctor
}

CondimentDecorator::~CondimentDecorator()
{
    //dtor
}

#ifndef MILK_H
#define MILK_H

#include "CondimentDecorator.h"


class Milk : public CondimentDecorator
{
    public:
        Milk(Beverage *beverage);
        ~Milk();
        std::string getDescription();
        double cost();
    protected:
    private:
        Beverage *beverage;
};

#endif // MILE_H


#include "Milk.h"
Milk::Milk(Beverage *beverage)
{
    this->beverage=beverage;
}

Milk::~Milk()
{
    //dtor
}

std::string Milk::getDescription()
{
    return beverage->getDescription()+", Milk";
}
double Milk::cost()
{
    return beverage->cost()+0.10;
}

#ifndef MOCHA_H
#define MOCHA_H

#include "CondimentDecorator.h"


class Mocha : public CondimentDecorator
{
    public:
        Mocha(Beverage *beverage);
        ~Mocha();
        std::string getDescription();
        double cost();
    protected:
    private:
        Beverage *beverage;
};

#endif // MOCHA_H

#include "Mocha.h"

Mocha::Mocha(Beverage *beverage)
{
    this->beverage=beverage;
}

Mocha::~Mocha()
{
    //dtor
}
double Mocha::cost()
{
    return 0.20+beverage->cost();
}
std::string Mocha::getDescription()
{
    return beverage->getDescription() +", Mocha";
}

#ifndef SOY_H
#define SOY_H

#include "CondimentDecorator.h"


class Soy : public CondimentDecorator
{
    public:
        Soy(Beverage *beverage);
        ~Soy();
        std::string getDescription();
        double cost();
    protected:
    private:
        Beverage *beverage;
};

#endif // SOY_H


#include "Soy.h"

Soy::Soy(Beverage *beverage)
{
    this->beverage=beverage;
}

Soy::~Soy()
{
    //dtor
}

std::string Soy::getDescription()
{
    return beverage->getDescription()+", Spy";
}

double Soy::cost()
{
    return 0.15+beverage->cost();
}

#ifndef WHIP_H
#define WHIP_H

#include "CondimentDecorator.h"


class Whip : public CondimentDecorator
{
    public:
        Whip(Beverage *beverage);
        ~Whip();
        std::string getDescription();
        double cost();
    protected:
    private:
        Beverage *beverage;
};

#endif // WHIP_H

#include "Whip.h"

Whip::Whip(Beverage *beverage)
{
    this->beverage=beverage;
}

Whip::~Whip()
{
    //dtor
}

std::string Whip::getDescription()
{
    return beverage->getDescription()+", Whip";
}

double Whip::cost()
{
    return 0.10+beverage->cost();
}

测试的主函数：

#include "Beverage.h"
#include "CondimentDecorator.h"
#include "DarkRoast.h"
#include "Decat.h"
#include "Espresso.h"
#include "HouseBlend.h"
#include "Milk.h"
#include "Mocha.h"
#include "Soy.h"
#include "Whip.h"
#include 
#include 
using namespace std;
int main()
{
    Beverage *beverage = new Espresso();
    cout<getDescription()<<" $"<cost()<getDescription()<<" $"<cost()<getDescription()<<" $"<cost()<

测试结果：

作者原创，转载请注明出处http://blog.csdn.net/lingyunjinzhu/article/details/8722884