From: Lyle Johnson <lyle@...>
Date: 2004-05-19T08:43:49+09:00
Subject: Re: FoX: removing widgets

Yuri Leikind wrote:

> When I need to delete some widget, I do it like this:
> 
> 	parent_obj.removeChild(obj_to_remove)
> 
> and then create and recalc
> 
> But, though the object deleted does not belong anywhere in the hierarchy of GUI objects,
> it still exists.

Correct. Calling removeChild() deletes the underlying C++ object. The 
Ruby object that was referring to that C++ object is no longer in use, 
but it hasn't been garbage-collected yet.

> I have a ObjectSpace.each_object() loop in my program iterating over some
> of FXObjects, setting new font and text. Naturally, doing anything to a removed object
> causes  error "This FXLabel (or FXWindow, or ...) * already released".

Yes. Accessing a Ruby object whose C++ partner is gone is a no-no.

> So, I have two questions:
> 
> 1) Is there a way to find out whether the object has already been released?

I don't guess so (it has never come up). If you were to add this request 
to the list of FXRuby bugs at SourceForge, I might add a way to find out 
this information in a future FXRuby release.

> 2) What else must be done to the FoX object that we want to delete, besides
> 		parent_obj.removeChild(obj_to_remove)

I guess you can try forcing the garbage collector to run immediately 
after the call to removeChild(), i.e.

	parent.removeChild(child)
	GC.start

Hope this helps,

Lyle