On Jun 26, 2008, at 1:46 AM, Rusty wrote:
> Hi.
> I found myself in a situation where I need to release external
> resources.
> In (some other Smalltalk) I use to do something like:
>
> MyClass new
> onFinalizeDo: #aSelector;
> yourself.
>
> If I underestand the documentation correctly, in VW I need to use
> WeakDictionary ... or Ephemerons.
>
> What if I don't need to keep a count of my finalizable objects ?
> I just need a method executed (or a block evaluated) when the object
> gets GC'd.
>
> Is there any way of doing so without using additional resources ?
> Or should I go ahead and create a WeakDictionary by hashs in a
> global or something and add each object on instanciation ?
There is a general purpose solution to this... kind of. There's a
package in the Open Repository called "Weaklings" that provides this
kind of behavior.
If you load the latest trunk version (version without a dot in the
name), then you can "wrap" your object with a "last rites" actions. So
you can do:
instance := MyClass new.
weakRef := instance withLastRites: [:obj | obj doCleanupStuff]
You send value to weakRef to get your instance. This pattern works
well when you want to hold an object, but hold it weakly and have some
cleanup happen when you quit holding it.
It doesn't work well if you want to just attach arbitrary finalization
actions to objects anonymously and not hold the weakRef alive some
where. The latest branch version of Weaklings, done by Boris Popov
provides a solution to this. I need to get integrate this to the
trunk, there were some method name changes I wanted to make, but other
than that, I think it should work fine for the anonymous case.
--
Travis Griggs
Objologist
"You A students, you'll be back soon teaching here with me. You B
students, you'll actually go on to be real engineers. You C students,
you'll go into management and tell the A and B students what to do." -
My Fluid Dynamics Professor whom I have yet to disprove
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