From: Andy Wingo <wingo@pobox.com>
Subject: Re: [1.6.4 GOOPS] no (next-method) in accessor?
Date: Mon, 26 Jul 2004 18:51:20 +0100 [thread overview]
Message-ID: <1090864279.1307.15.camel@localhost> (raw)
In-Reply-To: <Pine.LNX.4.56.0407251701450.30652@ariel>
Hey Steve,
I looked at your code. I'm no expert, but here's what I see.
On Sun, 2004-07-25 at 17:17 -0400, Steve Tell wrote:
> In a subclasse's accessor's #:slot-set! routine
Here's where you go wrong. The slot-set! routine is not a generic
function, nor does it belong to the accessor. Instead, these arguments
to `make-class' are used by the default compute-get-n-set generic, which
uses them to explicitly set the get/set functions for a class.
There is no MOP specified for get and set functions, though. If you
wanted to implement something like this, you could define a metaclass
for the root <ctrlpt> class that implements a custom compute-get-n-set
method.
Here's some code from (gnome gobject gtype), as an example:
(define-class <set-once-class> (<class>))
(define-method (compute-get-n-set (class <set-once-class>) s)
(case (slot-definition-allocation s)
((#:set-once)
(create-set-once-g-n-s class s #f)) ;; returns (list getter setter)
((#:set-once-each-subclass)
(create-set-once-g-n-s class s #t))
;; Chain up for the default allocation methods...
(else (next-method))))
;; We have to inherit from class because we're a metaclass. We do that
;; via <set-once-class>. We have #:set-once slots, so we also need to
;; have <set-once-class> as our metaclass.
(define-class <gtype-class> (<set-once-class>)
(gtype #:allocation #:set-once)
(gtype-class #:allocation #:set-once)
#:metaclass <set-once-class>)
In your case, since <ctrlpt> isn't a metaclass the supers list would be
empty.
Hope this helps,
--
Andy Wingo <wingo@pobox.com>
http://ambient.2y.net/wingo/
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prev parent reply other threads:[~2004-07-26 17:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-20 17:21 [GOOPS] Accessing a class slot Ludovic Courtès
2004-07-25 21:17 ` [1.6.4 GOOPS] no (next-method) in accessor? Steve Tell
2004-07-26 17:51 ` Andy Wingo [this message]
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