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

For the second problem, making setAngle virtual should do the trick.

For the first one, there are no easy solutions. Widget::move returns a Widget, which doesn't have a setText method. You could make a pure virtual setText method, but that'd be a pretty ugly solution. You could overload move() on the button class, but that'd be a pain to maintain. Finally, you could probably do something with templates. Perhaps something like this:

// Define a move helper function
template 
T& move(T& obj, Point& p){ return obj.move(p); };

// And the problematic line in your code would then look like this:
move(btn, Point(0,0)).setText("Hey");

I'll let you decide which solution is cleanest. But is there any particular reason why you need to be able to chain these methods?