Call a C++ base class method automatically

Question

I\'m trying to implement the command design pattern, but I\'m stumbling accross a conceptual problem. Let\'s say you have a base class and a few subclasses like in the examp

Answer 1

It looks as if you can benefit from the NVI (Non-Virtual Interface) idiom. There the interface of the command object would have no virtual methods, but would call into private extension points:

class command {
public:
   void operator()() {
      do_command();
      add_to_undo_stack(this);
   }
   void undo();
private:
   virtual void do_command();
   virtual void do_undo();
};

There are different advantages to this approach, first of which is that you can add common functionality in the base class. Other advantages are that the interface of your class and the interface of the extension points is not bound to each other, so you could offer different signatures in your public interface and the virtual extension interface. Search for NVI and you will get much more and better explanations.

Addendum: The original article by Herb Sutter where he introduces the concept (yet unnamed)