/**
  * Called before the form is generated
  *
  * Sets up a default rule for content tables so there are no
  * identical headlines
  *
  * @see NController::preGenerateForm();
  * @access public
  * @return null
  */
 function preGenerateForm()
 {
     $model =& $this->getDefaultModel();
     $fields = $model->fields();
     if (in_array('cms_headline', $fields)) {
         $model->form_rules[] = array('cms_headline', 'This headline is already being used', 'callback', array(&$this, 'uniqueHeadline'));
     }
     parent::preGenerateForm();
 }