programatically constructing the #'(setf accessor) function
Andreas Politz
assuming there is class foo with slot and accessor 'attribute'.
This makes it possible to read the value
(let ((reader 'attribute))
(funcall reader (make-instance 'foo)))
. But how do I best get at the corresponding #'(setf attribute) method
? Currently I am doing it like in the following code, but have a bad
feeling about it.
(defclass foo nil
((attribute
:accessor attribute
:initform 0)))
(defun make-undo-fn (object accessor)
(let ((value (funcall accessor object)))
(eval `(lambda nil
(funcall #'(setf ,accessor)
(quote ,value)
,object)))))
(setf obj (make-instance 'foo)
undo-fn (make-undo-fn obj 'attribute))
(attribute obj)
=> 0
(setf (attribute obj) 42)
=> 42
(funcall undo-fn)
=> 0
(attribute obj)
=> 0
-ap
Tobias C. Rittweiler
> Hi,
>
> assuming there is class foo with slot and accessor 'attribute'.
> This makes it possible to read the value
>
> (let ((reader 'attribute))
> (funcall reader (make-instance 'foo)))
>
> . But how do I best get at the corresponding #'(setf attribute) method
> ? Currently I am doing it like in the following code, but have a bad
> feeling about it.
(FDEFINITION `(setf ,attribute))
-T.
Andreas Politz
Thanks !
-ap