[Bese-devel] UCW beginners error; it.bese.ucw::place is unbound

[Matthew Danish]

On Wed, Feb 15, 2006 at 09:52:01AM +0000, Andrew Lawson wrote:
> Hello all
>     I've been playing with UCW for a day or so but have encountered an error that I can't seem to solve. I'm not sure whether I've not initialised something correctly ot whether I'm simply using the library on an unsupported platform (Lispworks 4.4.6, windows). The error I get is;
> 
> The slot IT.BESE.UCW::PLACE is unbound in the object #<IT.BESE.UCW-USER::MY-MODULE-CHOICE 21B457EC> (an instance of class #<IT.BESE.UCW:STANDARD-COMPONENT-CLASS IT.BESE.UCW-USER::MY-MODULE-CHOICE 21A614B4>).
> 
> Below is the code that causes this error when you click and it tries to call a new component, I've removed any code that seemed pointless and it still errors as before.
> 
> (in-package :it.bese.ucw-user)
> 
> (export 'startup)
> 
> (defun startup ()
>   (asdf:oos 'asdf:load-op :ucw.admin)
>   (asdf:oos 'asdf:load-op :ucw.examples)
>   (ucw:start-swank)
>   (ucw:create-server
>    :backend :aserve
>    :host "127.0.0.1"
>    :port 8080
>    :applications (list
>                   it.bese.ucw-user::*example-application*
>                   ucw::*admin-application*
>                   *website-application*)
>    :inspect-components nil
>    :log-root-directory (make-pathname 
>                         :name nil
>                         :type nil
>                         :directory (append (pathname-directory *load-truename*)
>                                            (list :up "logs"))
>                         :defaults *load-truename*)
>    :log-level it.bese.ucw::+info+
>    :start-p t))
> 
> ;(startup)
> 
> (defparameter *website-application*
>   (make-instance 'cookie-session-application :url-prefix "/website-application/"))
> 
> (defentry-point "index.ucw" (:application *website-application*) ()
>   (call 'my-simple-window-component))
> 
> 
> (defcomponent my-simple-window-component (simple-window-component)
>               ()
>               (:default-initargs
>                :title "My Website"))

(defcomponent my-simple-window-component (simple-window-component)
  ((body :accessor body :component (my-module-choice)))
  (:default-initargs :title "My Website"))

> 
> (defmethod initialize-instance :after ((self my-simple-window-component) &rest args)
>   (setf (ucw:window-component.stylesheet self) "http://localhost:8080/css/standard.css"))
> 
> (defmethod render ((com my-simple-window-component))
>   (<:div
>    :class "body"
>    (<:div
>     :class "title"
>     (<:div :class "header-1" "Website application"))
>    (<:div
>     :class "page"
>     (render (make-instance 'my-module-choice)))))

      (render (body com))


What this achieves is that by using :COMPONENT it automatically sets up
the PLACE and PARENT slots of MY-MODULE-CHOICE.  You could do this
without :COMPONENT by doing something like:

(defmethod initialize-instance :after 
      ((c my-simple-window-component) &rest initargs)
  (declare (ignore initargs))
  (setf (body c) (make-instance 'my-module-choice
                                :place (make-place (body c)) :parent c)))

I'm no expert, but I'm pretty sure this is all :COMPONENT ends up doing
anyhow.  Note that MAKE-PLACE is a macro which accepts a form as
argument, that form being the code which accesses the ``place'' of the
object (in SETF terminology).

Now when you use CALL-COMPONENT, there is a PLACE slot in the old
component for it to bind to the new component.

-- 
;; Matthew Danish -- user: mrd domain: cmu.edu
;; OpenPGP public key: C24B6010 on keyring.debian.org