设计模式入门,装饰着模式,c++代码实现

// test03.cpp : Defines the entry point for the console application.
//
//设计模式第3章 装饰者模式
#include "stdafx.h"
#include <string>
#include <iostream>
//#include <cstring>
using namespace std;
class Beverage
{
public:
    string description /*= "Unkown Beverage"*/;//只有静态整型常量数据成员能在类中初始化

public:
    virtual string getDescription()//必须为虚函数
    {
        return description;
    }

virtual double cost(){return 0;} ;//必须为虚函数

};

class CondimentDecorator : public Beverage
{
    virtual string getDescription(){return NULL;} ;
};

class Espresso : public Beverage
{
public:
    Espresso()
    {
        description = "Espresso";
    }

double cost(){
        return 1.99;
    }
};

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

double cost()
    {
        return .89;
    }
};

class DarkRoast : public Beverage
{
public:
    DarkRoast()
    {
        description = "Dark Roast Coffee";
    }

double cost()
    {
        return .99;
    }
};

class Mocha : public CondimentDecorator
{
    Beverage* beverage;

public:
    Mocha(Beverage* beverage)//必须为指针
    {
        this->beverage = beverage;
    }

string getDescription()
    {
        return beverage->getDescription() + ", Mocha";
    }

double cost()
    {
        return .20 + beverage->cost();
    }
};

class Whip : public CondimentDecorator
{
    Beverage* beverage;

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

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

double cost()
    {
        return .10 + beverage->cost();
    }
};

class Soy : public CondimentDecorator
{
    Beverage* beverage;

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

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

double cost()
    {
        return .15 + beverage->cost();
    }
};

int _tmain(int argc, _TCHAR* argv[])
{
    Beverage* beverage = new Espresso();
    cout<<beverage->getDescription() << " $ " << beverage->cost()<<endl;

Beverage* beverage2 = new DarkRoast();
    beverage2 = new Mocha(beverage2);//必须传递指针
    beverage2 = new Mocha(beverage2);
    beverage2 = new Whip(beverage2);
    //printf("%s %$ %f",beverage2->getDescription(),beverage2->cost());//printf 不能输出string类型
    cout<<beverage2->getDescription()<<" $ "<<beverage2->cost()<<endl;

Beverage* beverage3 = new HouseBlend();
    beverage3 = new Soy(beverage3);
    beverage3 = new Mocha(beverage3);
    beverage3 = new Whip(beverage3);
    //printf("%s %$ %f",beverage3->getDescription(),beverage3->cost());
    cout<<beverage3->getDescription()<<" $ "<<beverage3->cost()<<endl;
    return 0;
}