装饰者模式 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案。装饰者和被装饰者必须是一样的类型，也就是有共同的超类(超类我是设计成接口或者定义虚函数)，利用继承达到类型匹配。而不是利用继承获得行为。将装饰者与组件组合时，就是加入新的行为。所得的行为，不是继承自超类，而是由组合对象得来的。利用继承设计子类的行为，是在编译时静态决定的，而且所有的子类都会继承到相同的行为。然而，如果能够利用组合的做法扩展对象的行为，就可以运行时动态的扩展。通过动态的组合对象，可以写新的代码添加新功能，而无须修改现有代码。也就是开放-关闭原则。对扩展开放，对修改关闭。-----------------------------C++星巴滋咖啡实现——————————————————————————————————————

#include<iostream>
#include<string>
using namespace std;
class Beverage
{
public:
string describtion;
virtual string getDescribition()//抽象主键，如果不设计成virtural,并不能动态的改变
{
return describtion;
}
virtual double cost()=0;
virtual ~Beverage(){}
};
class CondimentDecorator:public Beverage  //装饰组件抽象类
{
public:
virtual string getDescribition()=0;//装饰者与被装饰者必须有一样的类型，利用继承达到类型匹配
};
class Expresso :public Beverage//具体组件
{
public:
Expresso()
{
describtion="Expresso";
}
double cost()
{
return 1.99;
}
};
class DarkRost :public Beverage
{
public:
DarkRost()
{
describtion="DarkRost";
}
double cost()
{
return 0.99;
}
};
class HouseBlend:public Beverage
{
public:
HouseBlend()
{
describtion="HouseBlend";
}
double cost()
{
return 0.89;
}
};
class Mocha:public CondimentDecorator//具体装饰者组件
{
private:
Beverage *beverage;
public:
Mocha(Beverage *beverage)
{
this->beverage=beverage;
}
string getDescribition()
{
return beverage->getDescribition() + " ,Mocha";
}
double cost()
{
return 0.20+beverage->cost();
}
};
class Whip:public CondimentDecorator
{
private:
Beverage *beverage;
string addstr;
public:
Whip(Beverage *beverage)
{
this->beverage=beverage;
}
string getDescribition()
{

return beverage->getDescribition()+" ,Whip";
}
double cost()
{
return 0.1+beverage->cost();
}
};
class Soy:public CondimentDecorator
{
private:
Beverage *beverage;
public:
Soy(Beverage *beverage)
{
this->beverage=beverage;
}
string getDescribition()
{
return beverage->getDescribition()+" ,Soy";
}
double cost()
{
return 0.15+beverage->cost();
}
};
int main()
{
Beverage *beverage=new Expresso();
cout<<beverage->getDescribition()<<" $"<<beverage->cost()<<endl;
Beverage *beverage1=new DarkRost();
beverage1=new Mocha(beverage1);
beverage1=new Mocha(beverage1);
beverage1=new Whip(beverage1);
cout<<beverage1->getDescribition()<<" $"<<beverage1->cost()<<endl;
delete beverage;
delete beverage1;
return 0;
}