/**
  * Fetch all users that will be exported
  *
  * @access private
  * 
  */
 private function fetchUsers()
 {
     $this->readCourseSpecificFieldsData();
     if ($this->settings->enabled('admin')) {
         $this->user_ids = $tmp_ids = $this->members->getAdmins();
         $this->readCourseData($tmp_ids);
     }
     if ($this->settings->enabled('tutor')) {
         $this->user_ids = array_merge($tmp_ids = $this->members->getTutors(), $this->user_ids);
         $this->readCourseData($tmp_ids);
     }
     if ($this->settings->enabled('member')) {
         $this->user_ids = array_merge($tmp_ids = $this->members->getMembers(), $this->user_ids);
         $this->readCourseData($tmp_ids);
     }
     if ($this->settings->enabled('subscribers')) {
         $this->user_ids = array_merge($tmp_ids = $this->members->getSubscribers(), $this->user_ids);
         $this->readCourseData($tmp_ids, 'subscriber');
     }
     if ($this->settings->enabled('waiting_list')) {
         include_once 'Modules/Course/classes/class.ilCourseWaitingList.php';
         $waiting_list = new ilCourseWaitingList($this->obj_id);
         $this->user_ids = array_merge($waiting_list->getUserIds(), $this->user_ids);
     }
     // Sort by lastname
     $this->user_ids = ilUtil::_sortIds($this->user_ids, 'usr_data', 'lastname', 'usr_id');
     // Finally read user profile data
     $this->user_profile_data = ilObjUser::_readUsersProfileData($this->user_ids);
 }