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- Subject: Re: Post-notification of access in metatable?
- From: Jamie Webb <j@...>
- Date: Thu, 29 Jul 2004 13:50:42 +0100
On Thu, Jul 29, 2004 at 01:07:38PM +0200, David Anderson wrote:
> Hi all,
> I am writing some lua glue to keep the values in a (minimal) structure
> in the C core in sync with the corresponding values in a (much bigger)
> table in the lua environment. At first I had thought I could use the
> __index (via a proxy table) element of the metatable to trigger
> callbacks in the C code whenever the values I monitor are accessed.
> However, the __index function gets called before the values are actually
> updated (makes sense), so at that stage I don't know if I need to call
> the C funcs (has the value changed?), and I don't know the new value, as
> it only gets affected after __index runs through.
> Looking through the manual and book, I can't find any metatable entry
> that would act as a postnotification, something like:
__newindex is exactly what you want. Remember that your proxy table is
empty (or should be :-), so any 'modification' looks to Lua like you
are creating a new table entry.
-- Jamie Webb