On Tue, 20 Apr 2004 14:11:06 -0600 (MDT), Jim Prewett <[EMAIL PROTECTED]> wrote:
> (defclass counted-class ()
> ((counter :initform 0)))
>
> (defmethod make-instance :after ((counted-class counted-class)) &rest args)
> (incf (slot-value counted-class 'counter)))
There should only be one closing paren after COUNTED-CLASS.
> the instances that are returned always have 0 in the counter slot.
>
> any ideas?
MAKE-INSTANCE dispatches on the class not on the object, i.e. to have
it called when a COUNTED-CLASS object is created you want something
like
(defmethod make-instance :after
((counted-class (eql 'counted-class)) &rest args)
but what you actually want is an :AFTER method for
INITIALIZE-INSTANCE:
* (defclass counted-class ()
((counter :initform 0)))
#<STANDARD-CLASS COUNTED-CLASS {486666CD}>
* (defmethod initialize-instance :after
((object counted-class) &rest init-args)
(declare (ignore init-args))
(incf (slot-value object 'counter)))
#<Standard-Method INITIALIZE-INSTANCE :AFTER (COUNTED-CLASS) {4866AA8D}>
* (describe (make-instance 'counted-class))
#<COUNTED-CLASS {4866D05D}> is an instance of class #<Standard-Class COUNTED-CLASS
{486627D5}>:
The following slots have :INSTANCE allocation:
COUNTER 1
Cheers,
Edi.
