Re: GC method for objects

["Adam D. Moss" <adam@...>]

Michael Cumming wrote:
>  From what I understand from the archives and my own testing, there is 
> no way for an object (table) to catch the GC?
>  
> The reason for wanting to do this is for use with Luacom.  Some COM 
> objects need to have their Quit (or whatever) method called before you 
> dispose of them.
>  
> So is there anyway to catch the __gc without resorting to userdata?

There's a hacky and inconvenient way which does involve userdata, but
userdata that can be manufactured from a central place (i.e. your
tables gets to stay as tables without having to userdatify your
various object types individually).

In short, what you do is create a weak-valued table which maps
from dummy created-on-demant heavyuserdata to your {}s - the __gc
sits on the userdata and thus indirectly gets called when the {}
becomes collectable.  You then need a way to map back from the
userdata to the table, so the __gc func can find the table in
question.  (Details of that omitted because I can't understand my
own code for this, this late at night.)

It's pretty disgusting... I'd quite like a working __gc on
tables too. :)

--Adam
--
Adam D. Moss   -   adam@gimp.org