materio-d8/web/modules/custom/materio_sapi/src/ThesaurusRefComputed.php

<?php

namespace Drupal\materio_sapi;

use Drupal\Core\Field\EntityReferenceFieldItemList;
use Drupal\Core\TypedData\ComputedItemListTrait;

class ThesaurusRefComputed extends EntityReferenceFieldItemList {
  use ComputedItemListTrait;

  /**
   * Computed related blog posts.
   */
  protected function computeValue() {
    $field_name = $this->getName();
    switch ($field_name) {
      case 'thesaurus_0':
        $delta = 0;
        break;
      case 'thesaurus_1':
        $delta = 1;
        break;
      case 'thesaurus_2':
        $delta = 2;
        break;
      case 'thesaurus_3':
        $delta = 3;
        break;
      case 'thesaurus_4':
        $delta = 4;
        break;
      default:
        $delta = -1;
        break;
    }

    $thes_terms = $this->getParent()->getValue()->get('field_thesaurus')->getValue();

    if (count($thes_terms) > 0) {
      if (isset($thes_terms[$delta])) {
        $term = $thes_terms[$delta];
        $this->list[0] = $this->createItem(0, $term);
        $t="t";
      }
    }
  }
}