装饰者模式 C++实现

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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;}

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