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Re: equivalent of "this" in goops?


From: Andreas Rottmann
Subject: Re: equivalent of "this" in goops?
Date: Thu, 17 Feb 2005 00:07:40 +0100
User-agent: Gnus/5.1002 (Gnus v5.10.2) Emacs/21.3 (gnu/linux)

Greg Troxel <address@hidden> writes:

> I'm using guile 1.6.x,and doing network mapping.
>
> In a class representing a node, I want to have a slot with an
> init-thunk, and I would like to call a procedure with the class object
> as an argument.  The slot holds a class object which is basically a
> hash table of links in a network, and it needs the node object so it
> can hash on 'other end node id'.
>
> So, I'd like to pass 'this' in c++ terms, and I don't see how to do
> that from reading goops.info.  I realize there are issues with the
> class not being fully initialized, and in my case that's safe since
> I'm just storing the object in a variable and not using it until a
> link is added, which doesn't happen during object initialization.
> Thus I realize that what I want to do is vaguely unschemely.

FWICT (not being a GOOPS expert), this is not possible without
extending GOOPS: the init-thunk of a slot is specified at class
creation time, and the earliest time "this" is avaiable is in the
"initialize" generic. However, since the init-thunk is called at
initialization time, "this" would be available at the time it is run,
but there is no way to pass it, since the init-thunk, is, well, a
thunk ;). I could imagine a init-function (name to be argued), which
gets passed all arguments from "initialize" could be a useful
extension.

> My fallback is to initialize the linkset on first use, or after object
> createion, or something like that.
>
Given a GOOPS with this hypothetical extension is far from official
release ;), a workaround is probably the only feasibly short-term
solution (given my assumtion that this is not possible with current
GOOPS).

Cheers, Rotty
-- 
Andreas Rottmann         | address@hidden      | address@hidden | address@hidden
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