装饰模式（Decorator）

2015/4/28
装饰模式（Decorator）,动态的给一个对象添加一些额外的职责，就增加功能来说，装饰模式比生成子类更为灵活。—大话设计模式

#include <vector>
#include <iostream>
using namespace std;
/*基类*/
class Component{
    public:
        virtual void Operation(){
            cout<<"的";
        };
};
/*被装饰类*/ 
class ConcreteComponent:public Component{
    public:
    void Operation(){
        Component::Operation();
    cout<<"小瞿"<<endl; 
    }
};
/*装饰类的基类*/ 
class Decorator:public Component{
    private:
        /*
        此处为了让装饰类连成环并且可以指向装饰类也可以指向被装饰类
        所以使用了同一个基类指针形成多态 
        */
        Component *pc;
    public:
        Decorator(Component *p){ this->pc=p;}
    virtual void Operation(){
        pc->Operation();
    }
};
class ConcreteDecoratorA:public Decorator{
    public:
        ConcreteDecoratorA(Component *t):Decorator(t){
        }
        void Operation()
        {
            cout<<"打着领带";
            Decorator::Operation();
        }
}; 
class ConcreteDecoratorB:public Decorator{
    public:
        ConcreteDecoratorB(Component *t):Decorator(t){
        }
        void Operation()
        {
            cout<<"身穿西装"; 
            Decorator::Operation();
        }
}; 
class ConcreteDecoratorC:public Decorator{
    public:
        ConcreteDecoratorC(Component *t):Decorator(t){
        }
        void Operation()
        {
            cout<<"穿着皮鞋"; 
            Decorator::Operation();
        }
}; 
int main(void)
{
    Component *p=new ConcreteComponent();
    Component *p1=new ConcreteDecoratorC(p);
    Component *p2=new  ConcreteDecoratorB(p1);
    Component *p3=new ConcreteDecoratorA(p2);
    p3->Operation();
    return 0;
}

何时使用装饰模式：当系统有了新的功能需要添加的时候，就是向旧的类添加新的修饰代码。
但是具有缺点：装饰模式顺序很重要