public function notifyUsers(Notification $notification, $userIds)
    {
        if (count($userIds) > 0) {
            foreach ($userIds as $userId) {
                if (null !== $userId && $notification->getUserId() !== $userId) {
                    $notificationViewer = new NotificationViewer();
                    $notificationViewer->setNotification($notification);
                    $notificationViewer->setViewerId($userId);
                    $notificationViewer->setStatus(false);
                    $this->getEntityManager()->persist($notificationViewer);
                }
            }
        }
        $this->getEntityManager()->flush();

        return $notification;
    }