/**
  * @return form_ListService
  */
 public static function getInstance()
 {
     if (self::$instance === null) {
         self::$instance = self::getServiceClassInstance(get_class());
     }
     return self::$instance;
 }
 /**
  * @param form_persistentdocument_recipientGroupList $document
  * @param Integer $parentNodeId Parent node ID where to save the document (optionnal => can be null !).
  * @return void
  */
 protected function preSave($document, $parentNodeId = null)
 {
     $document->setFieldName(form_FormService::RECIPIENT_GROUP_FIELD_NAME);
     $document->setDataSource(list_ListService::getInstance()->getDocumentInstanceByListId('modules_form/recipientgrouplist'));
     $document->setRequired(true);
     parent::preSave($document, $parentNodeId);
 }
 /**
  * @return form_persistentdocument_list
  */
 protected function initPersistentDocument()
 {
     return form_ListService::getInstance()->getNewDocumentInstance();
 }