[Bese-devel] UCW guidance

[Vladimir Sekissov]

Good day,

jan> I've encountered the next snag: how do I error-check a form and feed it
jan> back to the user if it contains errors?
jan> 
jan> An example to that effect would be very, very helpful -- I couldn't find
jan> one in the examples.

I'd posted code for `status-bar-mixin' to mailing list which I
use for such purposes:

http://common-lisp.net/pipermail/bese-devel/2005-June/000396.html

I use it in form as:

(defun collect-error (condition)
  (flet ((error-collector (error-tag error)
            (show-message (format nil "~a"  error) :severity error-tag)))
     (let ((restart (find-restart 'collect-error)))
        (when restart (invoke-restart restart
                                      #'error-collector
                                      condition)))))

(defmacro with-collect-error (body-form on-error-form &key (error-tag :error))
  (let ((error-collector (gensym))
        (condition (gensym)))
    `(restart-case ,body-form
       (collect-error (,error-collector ,condition)
         (funcall ,error-collector ,error-tag ,condition)
         ,on-error-form))))

....

  (handler-bind ((error #'collect-error))
     (dolist (field (form-fields form))
        (with-collect-error
           (validate-form-field field)
           nil)))

Best Regards,
Vladimir Sekissov