Re: glist manipulation and reference count

["Brian J. Tarricone" <bjt23 cornell edu>]

[Note that your question is probably more appropriate for 
gtk-app-devel-list or gtk-list; this list is for the development *of* 
glib/gtk itself, not about developing apps that *use* glib/gtk.]

On 05/14/2009 08:47 PM, walty wrote:

> However, one thing that surprised me is that, when I do "g_list_append" or
> "g_list_prepend", it does not automatically add the reference count of the
> stored GObject (unlike objective-C).

GList is a generic container that you can put any kind of pointer into. 
 It doesn't know about GObjects or reference counting.  In fact libglib 
(where GList is implemented) doesn't even link to libgobject.

> So do I need to explicitly add the reference count each time the GObject is
> inserted? and reduce the reference count when the object is removed? That
> seems quite cumbersome to me.

That depends on how you want to use it.  If you can be sure no one else 
will destroy the object while you're using it in the list, then no, you 
don't.

I've used both glib/gobject and NSArray/NSDictionary/etc., and 
personally I don't find either approach to be better or worse.  I rarely 
need to increase refcnts on GObjects when I store them in lists, but 
perhaps others have different use cases that do require this.

> Or can I add some function pointer to generalize this? Is there some kind of
> best practice on this?

If you add the objects in one shot, you can do something like this after 
you've added all objects:

g_list_foreach(list, (GFunc)g_object_ref, NULL);

Of course that iterates over the entire list, so it would be a bit slow 
on a large list.  You can always ref the objects as you insert them, e.g.:

list = g_list_append(list, g_object_ref(obj));

Of course you have to do something similar with _unref() when you remove 
items from the list or destroy the list.

	-brian