Method chaining + inheritance don't play well together?

Question

Consider:

// member data omitted for brevity

// assume that \"setAngle\" needs to be implemented separately
// in Label and Image, and that Button does need         


        

Answer 1

I think (I haven't tested it) this will do it using templates:

template struct TWidget {
    T& move(Point newPos) { pos = newPos; return (T&)*this; }
};

template struct TLabel : TWidget { ... }

struct Label : TLabel { ... }

struct Button : TLabel { ... }

Notes:

• Any/every base class needs to be a template, with a separate non-template leaf class at the top (contrast the LabelT and Label classes).
• The cast could be a dynamic_cast if you like.
• Instead of casting the "return *this", the base class could contain a T& as a data member (the derived class would pass this to the base class' constructor), which would be an extra data member, but which avoids a cast and I think may permit composition instead of or as well as inheritance.