[Openmcl-devel] [off-topic] Adding a slot to a class using the MOP
ron at flownet.com
Mon Apr 22 23:29:07 PDT 2013
Why not this?
(defmethod ensure-class-using-class :before (class name &rest args)
(setf (get 'class-info name) (list* class args)))
(defun add-slot (class-name slotspec)
(destructuring-bind (class . args) (get 'class-info class-name)
(push slotspec (getf args :direct-slots args))
(apply 'ensure-class-using-class class class-name args)))
It seems to work:
? (defclass foo () (x y z))
? (add-slot 'foo '(:name q))
? (describe (make-instance 'foo))
Class: #<STANDARD-CLASS FOO>
Wrapper: #<CCL::CLASS-WRAPPER FOO #x3020028B9EBD>
On Apr 22, 2013, at 1:23 PM, Pascal Costanza wrote:
> Check out AspectL, it provides exactly what you want.
> However, it's also worthwhile spending some time on thinking about whether there is a better design for your problem. Adding slots like this creates a lot of problems. Maybe a typical hash table based meta class already provides what you need...
> Sent from my iPad
> On 22 Apr 2013, at 19:32, Ron Garret <ron at flownet.com> wrote:
>> Apologies for the non-CCL-related question, but c.l.l. is slow today and I'm really stuck on this.
>> I need to dynamically add a slot to a class using the MOP. There doesn't seem to be a standard add-slot method, so I figure I need to use something like ensure-class. To do that, I need to reconstruct the argument to :direct-slots from the existing class definition so I can add a slot without disturbing the existing slots. Before I went down this rabbit hole I thought I'd ask: is there a better/easier way to do this? Surely I'm not the first person to want to do this.
>> Many thanks,
>> Openmcl-devel mailing list
>> Openmcl-devel at clozure.com
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