//操作類
class action
{
public:
  virtual void do()=0;
};

class write : public action
{
public:
   void do(){ count << "to write\n";}
};

class draw : public action
{
public:
  void do() { count << "to draw\n";}
};

class gift : public action
{
public:
  void do {count << "to gift\n";}
};

//實(shí)體類
class pen
{
public:
  pen(): m_pAction(NULL){}
  virtual ~pen(){ delete m_pAction;}
  virtual void use();
  void setaction(action* pAction){m_pAction = pAction;}
protected:
  action* m_pAction;
};

class pencil : public pen
{
  void use()
  { 
    cout << "use pencil ";
    m_pAction.do(); 
  }
};

class brush : public pen
{
  void use()
  { 
    cout << "use brush ";
    m_pAction.do(); 
  }
};

class goldenpen : public pen
{
  void use()
  { 
    cout << "use goldenpen ";
    m_pAction.do(); 
  }
};

int main
{
  ballpen inHand;
  inHand.setaction(new gift());
  inHand.use();
}