Decorator

Decorator 用來將功能擴充
先定義一個介面,Decorator具有該介面,且將之擴充功能
Java的IO用到很多這個Pattern

class Base {
public:
 virtual void Action(){}
};

class Decorator : public Base {
private:
 Base* base;
public:
 Decorator(){};

 Decorator(Base* base)
 {
  this->base = base;
 }

 virtual void Action()
 {
  this->base->Action();
  this->Add_on();
 }

 virtual void Add_on(){}
};

class BaseClass : public Base {
public:
 virtual void Action()
 {
  cout << "Action:\n";
 }
};

class GoodDecorator : public Decorator {
public:
 GoodDecorator(Base* base) : Decorator(base)
 {}

 virtual void Add_on()
 {
  cout << "Good\n";
 }
};

class BadDecorator : public Decorator {
public:
 BadDecorator(Base *base) : Decorator(base)
 {}

 virtual void Add_on()
 {
  cout << "Bad\n";
 }
};


int main()
{
 BaseClass *bs = new BaseClass();
 GoodDecorator *good = new GoodDecorator(bs);
 BadDecorator *bad = new BadDecorator(bs);
 
 bs->Action();
 good->Action();
 bad->Action();
 
 return 0;
}