装饰模式是一种经典的类功能扩展模式，其精髓在装饰类使用继承加聚合的方式获得接口和要实现对象，然后通过自己实现扩展接口

作用
装饰模式通过装饰类动态地将责任附加到对象上，若要扩展功能，无需通过继承增加子类就能扩展对象的新功能，提供了比继承更有弹性的替代方案，避免了子类数量膨胀带来的系统臃肿。

类视图

代码实现

class Component{public: Component(){} virtual ~Component(){} virtual void operation() = 0;};class ConcreteComponentA : public Component{public: ConcreteComponentA(){} ~ConcreteComponentA(){} void operation() { fprintf(stderr, "ConcreteComponentA's operation!\n"); }};class ConcreteComponentB : public Component{public: ConcreteComponentB(){} ~ConcreteComponentB(){} void operation() { fprintf(stderr, "ConcreteComponentB's operation!\n"); }};class Decorator : public Component{public: Decorator() :mComponent(NULL){} virtual ~Decorator(){} virtual void operation() { if (mComponent) mComponent->operation(); } virtual void setComponent(Component* pComponent) { mComponent = pComponent; }protected: Component* mComponent;};class ConcreteDecoratorE : public Decorator{public: ConcreteDecoratorE (); virtual ~ConcreteDecoratorE (); virtual void addBehavior() { mComponent->operation(); fprintf(stderr, "ConcreteDecoratorE's addBehavior!\n"); }};class ConcreteDecoratorF : public Decorator{public: ConcreteDecoratorF (); virtual ~ConcreteDecoratorF (); virtual void addBehavior() { operation(); fprintf(stderr, "ConcreteDecoratorF's addBehavior!\n"); }};int main(){ ConcreteComponentB *pComponent = new ConcreteComponentB(); ConcreteDecoratorF decorator; decorator.setComponent(pComponent); decorator.addBehavior();}

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