class PrerenderList

Permissions.php in drupal/core/modules/user/lib/Drupal/user/Plugin/views/field/Permissions.php

Definition of Drupal\user\Plugin\views\field\Permissions.

Roles.php in drupal/core/modules/user/lib/Drupal/user/Plugin/views/field/Roles.php

Definition of Drupal\user\Plugin\views\field\Roles.

TaxonomyIndexTid.php in drupal/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/views/field/TaxonomyIndexTid.php

Definition of Drupal\taxonomy\Plugin\views\field\TaxonomyIndexTid.

class PrerenderList extends FieldPluginBase {

  /**
   * Stores all items which are used to render the items.
   * It should be keyed first by the id of the base table, for example nid.
   * The second key is the id of the thing which is displayed multiple times
   * per row, for example the tid.
   *
   * @var array
   */
  var $items = array();
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['type'] = array(
      'default' => 'separator',
    );
    $options['separator'] = array(
      'default' => ', ',
    );
    return $options;
  }
  public function buildOptionsForm(&$form, &$form_state) {
    $form['type'] = array(
      '#type' => 'radios',
      '#title' => t('Display type'),
      '#options' => array(
        'ul' => t('Unordered list'),
        'ol' => t('Ordered list'),
        'separator' => t('Simple separator'),
      ),
      '#default_value' => $this->options['type'],
    );
    $form['separator'] = array(
      '#type' => 'textfield',
      '#title' => t('Separator'),
      '#default_value' => $this->options['separator'],
      '#states' => array(
        'visible' => array(
          ':input[name="options[type]"]' => array(
            'value' => 'separator',
          ),
        ),
      ),
    );
    parent::buildOptionsForm($form, $form_state);
  }

  /**
   * Render all items in this field together.
   *
   * When using advanced render, each possible item in the list is rendered
   * individually. Then the items are all pasted together.
   */
  protected function renderItems($items) {
    if (!empty($items)) {
      if ($this->options['type'] == 'separator') {
        return implode($this
          ->sanitizeValue($this->options['separator'], 'xss_admin'), $items);
      }
      else {
        $item_list = array(
          '#theme' => 'item_list',
          '#items' => $items,
          '#title' => NULL,
          '#type' => $this->options['type'],
        );
        return drupal_render($item_list);
      }
    }
  }

  /**
   * Return an array of items for the field.
   *
   * Items should be stored in the result array, if possible, as an array
   * with 'value' as the actual displayable value of the item, plus
   * any items that might be found in the 'alter' options array for
   * creating links, such as 'path', 'fragment', 'query' etc, such a thing
   * is to be made. Additionally, items that might be turned into tokens
   * should also be in this array.
   */
  public function getItems($values) {
    $field = $this
      ->getValue($values);
    if (!empty($this->items[$field])) {
      return $this->items[$field];
    }
    return array();
  }

  /**
   * Determine if advanced rendering is allowed.
   *
   * By default, advanced rendering will NOT be allowed if the class
   * inheriting from this does not implement a 'renderItems' method.
   */
  protected function allowAdvancedRender() {

    // Note that the advanced render bits also use the presence of
    // this method to determine if it needs to render items as a list.
    return method_exists($this, 'render_item');
  }

}