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Allegro CL version 9.0
This page is new in 9.0.


Arguments: window standard-object slot-name value

This generic function is called whenever a user attempts to enter a new slot value in an object-editor dialog or a class-grid widget. If it returns true then the new value is accepted, and if it returns nil then the value is rejected and the object-editor widget or the class-grid cell will continue to show the pre-edited slot value.

The default method simply returns t to allow any edit. An application could define one or more methods that override the default method to check whether the user has entered an invalid value, returning nil if so. A method could also show an error dialog explaining why the value was rejected, for example.

window will be either an object-editor dialog or the parent window that a class-grid is on. This is a suitable window to serve as the owner of an error dialog.

standard-object will be the object that is currently displayed in an object-editor dialog, or in the selected row of a class-grid widget.

slot-name will be the symbol that names the slot that is edited by the particular object-editor widget or class-grid column in which the user is currently editing a value.

value will be the newly edited value that the user is attempting to write into the slot.

Here is a simple example that allows a particular slot to contain only a string where every character is a letter. (The class does not need to be a persistent AllegroCache class, but that is typical when using an object-editor or class-grid.)

(defclass my-thing ()
  ((foo :accessor foo :initform "" :initarg :foo))

(defmethod validate-edited-slot-value
    ((window basic-pane)(my-thing my-thing)(slot-name (eql 'foo)) value)
  (cond ((and (stringp value)
              (every #'alpha-char-p value))
        (t (pop-up-message-dialog
            window "Invalid Value"
	    #.(format nil "The value of the foo slot must be ~
                           a string that contains only letters.")
            warning-icon "~OK")

Copyright (c) 1998-2012, Franz Inc. Oakland, CA., USA. All rights reserved.
Documentation for Allegro CL version 9.0. This page is new in the 9.0 release.
Created 2010.1.21.

Allegro CL version 9.0
This page is new in 9.0.