/*
  For simple commands that aren’t undoable and don’t require arguments, 
  we can use a class template to parameterize the command’s receiver. 
  We’ll define a template subclass SimpleCommand for such commands. 
  SimpleCommand is parameterized by the Receiver type and 
  maintains a binding between a receiver object and an action stored as a pointer to a member function. 
 */

template <class Receiver>
class SimpleCommand : public Command {
public:
    typedef void (Receiver::* Action)();

    SimpleCommand(Receiver* r, Action a) :
        _receiver(r), _action(a) {}

    virtual void Execute();
private:
    Action _action;
    Receiver* _receiver;
};

/* The constructor stores the receiver and 
the action in the corresponding instance variables. 
Execute simply applies the action to the receiver. */

template <class Receiver>
void SimpleCommand<Receiver>::Execute () {
    (_receiver->*_action)();
}