/**
  * Load all active notificationServices into static array which are active and of correct type
  *
  * @return void
  */
 protected static function loadAllCaretakerNotificationServices()
 {
     self::$notificationServiceInstances = array();
     foreach ($GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['caretaker']['notificationServices'] as $serviceKey => $notificationService) {
         $instance = t3lib_div::getUserObj($GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['caretaker']['notificationServices'][$serviceKey]);
         if ($instance instanceof tx_caretaker_NotificationServiceInterface && $instance->isEnabled()) {
             self::$notificationServiceInstances[$serviceKey] = $instance;
         }
     }
 }