Re: Class Members and the Class Finalize Function

[Tim Janik <timj gtk org>]

On Wed, 14 Feb 2001, Eric Lemings wrote:

> I'm using GLib 2.0 to create a "Gizmo" class that has a "GizmoPart"
> object as one of the members of the Gizmo instance structure.  For most
> instances of Gizmo, the GizmoPart object member is the same kind of
> object.  Rather than create separate GizmoPart objects for each Gizmo
> object, I'd prefer to create a common GizmoPart object and share it
> between Gizmo objects that use that kind of GizmoPart object.
>
> I add a static member to the Gizmo class structure and create it in the
> class initialize function.  (I could store it with static scope within
> the source file but then how could I destroy it?)  The logical place to
> destroy (i.e., unreference, release, free) the shared class object is in
> the class finalize function.  But the type system for some reason gives
> a warning about "class finalize function specified for static type" and
> refuses to register the class.
>
> Why is that and what should I do about it?

unless you inroduce a dynamic type that uses the GTypePlugin interface,
your type's class will never be destroyed, therefore it doesn't
need a finalizer.
if you're worried about extra allocation, the best thing is probably to
create gizmopart on demand and use normal reference counting on it:


ref_gizmopart ()
{
  if (!static_gizmopart)
    static_gizmopart = g_object_new (G_TYPE_GIZMOPART,...);
  else
    g_object_ref (static_gizmopart);

  return static_gizmopart;
}

of course you want this global gizmopart object to reset
static_gizmopart to NULL when finalized (e.g. a qdata destroy
function), or if gizmopart is_a gtkobject, connect to ::destroy).


> Thanks,
> Eric.

---
ciaoTJ