The only way I have found to do custom validation on field collections is by prepending a validation hook to the element_validate property of the widget. Below is an example on how I did this.

/*
 * Adds a validation hook to the beginning of the #element_validate
 * to provide custom validation on the required fields within the
 * widget.
 */
function trip_planner_field_widget_form_alter(&$element, &$form_state, $context) {
  switch ($context['instance']['widget']['type']) {
    case 'field_collection_embed':
      // @todo check for field name
      array_unshift($element['#element_validate'], 'trip_planner_validate_line_item');
      break;
  }
}

/*
 * Validate our from and to destinations from our field collection
 * widget.  We need to use form_error on each field to fire off the
 * necessary errors.
 */
function trip_planner_validate_line_item($element, &$form_state, $form) {
  form_error($form['field_from_to'][LANGUAGE_NONE][0]['field_tee_time'], 'test');
}

If you have unlimited values, you will need to iterate over your container (which I will be doing next if anyone is interested). The reason why it needs to be done this way is because the function field_collection_field_widget_embed_validate() validates and submits all in once, so if you add a validation hook anywhere else, except before this function, it just gets ignored.

Comments

charlie-s’s picture

charlie-s CreditAttribution: charlie-s commented

Does the above code add the custom validation handler to every single embedded field collection on that site? I ask because I'm trying to properly add custom validation to field collections and am having a hard time, but the case 'field_collection_embed': appears to me that it would throw this on every embedded field collection widget.

iLLin’s picture

iLLin CreditAttribution: iLLin commented

Yea it should, you will just need to filter it inside the validate hook for your field collection.

erinclerico’s picture

erinclerico CreditAttribution: erinclerico commented

I would like to see your example of unlimited values - thank you very much.

I'm having some trouble getting at the correct approach with my implementation of hook_form_alter for the inline collection fields using dsm() - 

function schoolmeal_form_alter(&$form, $form_state, $form_id) {
  dsm ($form_id);
}

This returns nothing to the screen (except for the base node form id) so I'm a little in the dark in terms of exactly how to manipulate my $form (for the inline collections) for the validation I need to add.

Thank you in advance.

-Erin

darvanen’s picture

darvanen
he/him
Primary language English
Location Sydney, Australia
CreditAttribution: darvanen commented

I managed to iterate through and even target specific items in the field collection in Drupal 8 like this:

function MODULENAME_FORMID_form_validate(array &$form, \Drupal\Core\Form\FormStateInterface $form_state) {
  $items = $form_state->getValue('field_collection');
  foreach($item as $key => $item){
    if (is_int($key)){
      // Is there a file uploaded?
      $file = count($resource['field_document'][0]['fids']);
      // Is there a link?
      $link = (strlen($resource['field_link'][0]['uri']) ? 1 : 0);

      // Make sure there is one and only one value
      if ($file + $link != 1){
        $form_state->setError($form['field_collection']['widget'][$key], t('Error message'));
      }
    }
  }
}