RE: Composition vs. Deriviation in Gtkmm

["Gavin Lambert" <gavinl compacsort com>]

Quoth José Alburquerque:
> On Wed, 2012-11-07 at 13:34 -0600, kenton wilson gmail com wrote:
> > in the context of Gtkmm, is there a rationale for preferring derivation 
> > over composition (or vice-versa).
>
> From memory, I think the examples use a combination of inheritance and
> composition.  For example, a lot of the examples have their own window
> class that derives from Gtk::Window.  That's inheritance.  However,
> whenever a widget class in the examples includes a declaration of a
> widget that it uses in some way (maybe to form part of its own
> presentation), composition is being used in that case.  Both methods
> have their usefulness depending on what you want to accomplish and gtkmm
> supports both.

In other words, it's just figuring out whether a given object IS a thing or HAS a thing.  If it IS a window, then derive from Window.  If it HAS a helper widget, then it contains it.

It's not limited to gtkmm, it's standard practice in object-oriented design.