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;
}