Filter the list of entities referenced by "Entity reference revisions" field

Question

I have a content type "Slider" which uses an Entity reference revisions field named "Slides" to save reference to various paragraphs that are then displayed on the frontend as a hero slider.

Everything works fine but now we have received a request of filtering out the slides by a show/hide boolean flag in the slide paragraph. Adding a boolean field to each such paragraph is straightforward but how do I filter those paragraphs based on it? I'm assuming a Drupal hook that allows a function to filter out the referenced entities by some arbitrary criterion but I've been unable to find it.

I understand that this question relates to a 3rd party module but it is quite possible that a core Drupal hook could be used in this context.

Any help will be greatly appreciated.

Thanks.

Answer 1

I'd recommend doing this by creating a new Field Formatter by extending the default EntityReferenceRevisionsEntityFormatter (or extending whichever formatter you're using to display the paragraphs). If you're not sure how to create a field formatter, review the Create a custom field formatter documentation on d.o.

Specifically, you'll need to override the getEntitiesToView() method, something like this:

protected function getEntitiesToView(EntityReferenceFieldItemListInterface $items, $langcode) {
  $entities = parent::getEntitiesToView($items, $langcode);
  $allowed_entities = [];

  foreach($entities as $entity) {
    // Check if your show/hide checkbox is checked.
    // Note: I can't remember if this check is sufficient by itself.
    if (!$entity->my_show_hide_field->isEmpty()) {
      $allowed_entities[] = $entity;
    }
  }

  return $allowed_entities;
}

Lastly, you'll need to configure your entity reference revisions field to use this new formatter.