[Bese-devel] EVAL: variable SELF has no value

[Pascal J.Bourguignon]

I've got a simple render-on method that just calls another component:

(defmethod render-on ((res response) (compo user-admin))
  (call 'not-implemented-yet
        :message (_ "Administration des utilisateurs")))


(defcomponent not-implemented-yet (widget-component)
  ((message  :accessor not-implemented-yet.message
             :initform nil
             :initarg :message
             :documentation "A message which will be presented to the user"))
  (:default-initargs
   :title (_ "Pas encore implémenté" "Window Title")
   :stylesheet "stylesheet.css")
  (:metaclass standard-component-class)
  (:documentation "Not implemented yet."))


(defmethod render-on ((res response) (compo not-implemented-yet))
  (<:div
    :id "not-implemented-yet"
    (when (not-implemented-yet.message compo)
      (<:h2 (<:as-html (not-implemented-yet.message compo))))
    (<:p (<:as-html
          (_ "Désolé, cette fonction n'est pas encore implémentée.")))
    (<ucw:form
     (button (_ "Retour" "Button") (answer-component compo nil)))))


Then, when the first component is to be rendered, I obtain instead a
backtrace with the top of stack being:

EVAL frame for form ((LAMBDA (RES COMPO) 
                     (DECLARE (SYSTEM::SOURCE
                               ((RES COMPO)
                                 (DECLARE (IGNORABLE RES COMPO)) 
                                 (BLOCK RENDER-ON
                                   (CALL 'NOT-IMPLEMENTED-YET
                                      :MESSAGE
                                      (_ "Administration des utilisateurs"))))))
                     (DECLARE (IGNORABLE RES COMPO))
                     (CALL-COMPONENT SELF (MAKE-INSTANCE 'NOT-IMPLEMENTED-YET
                         :MESSAGE "Administration des utilisateurs")))
                     #:G13176 #:G13177)


By the same token, I cannot write (ANSWER result) because this macro
expands to an expression refering SELF, so I have to write:

  (ANSWER-COMPONENT compo result)


Do I do something wrong or should I just avoid these macros?

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
Until real software engineering is developed, the next best practice
is to develop with a dynamic system that has extreme late binding in
all aspects. The first system to really do this in an important way
is Lisp. -- Alan Kay