MapFieldItemList.php

<?php

namespace Drupal\Core\Field;


/**
 * Defines an item list class for map fields.
 */
class MapFieldItemList extends FieldItemList {

  /**
   * {@inheritdoc}
   */
  public function equals(FieldItemListInterface $list_to_compare) {
    $count1 = count($this);
    $count2 = count($list_to_compare);
    if ($count1 === 0 && $count2 === 0) {

      // Both are empty we can safely assume that it did not change.
      return TRUE;
    }
    if ($count1 !== $count2) {

      // The number of items is different so they do not have the same values.
      return FALSE;
    }

    // The map field type does not have any property defined (because they are
    // dynamic), so the only way to evaluate the equality for it is to rely
    // solely on its values.
    $value1 = $this
      ->getValue();
    $value2 = $list_to_compare
      ->getValue();
    return $value1 == $value2;
  }

}