Re: glist manipulation and reference count

[walty <walty8 gmail com>]

Hi Brian,

Thanks for the reply. 

I think I had some confusion here, I thought GObject is part of GLib, and
apparently that's not true.

The scenario is that I need to temporary update the screen, and store the
old widgets on the list. So if I did not explicitly add the ref count, the
objects would be destroyed once they are removed from parent (even if I
stored the object reference in g_list).

I think I would use a general helper function for list insert & remove then.
Just want to make sure I did not miss something obvious.

And I would move my future questions to gtk-app-devel-list  :P

Thanks again.


walty


Brian J. Tarricone wrote:
> 
> [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
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> 
> 

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