How to apply default sorting for child objects of the type Tx_Extbase_Persistence_ObjectStorage

child-repository.php

/**
 *
 *
 * @package nboevents
 * @license http://www.gnu.org/licenses/gpl.html GNU General Public License, version 3 or later
 *
 */
class Tx_Nboevents_Domain_Repository_EventRepository extends Tx_Extbase_Persistence_Repository {
	/**
	 * defaultOrderings
	 *
	 * @var array
	 */
	protected $defaultOrderings = array(
	    'date' => Tx_Extbase_Persistence_QueryInterface::ORDER_ASCENDING,
	);
	
	
	/**
	 * findByCourse
	 *
	 * @param $uid
	 * @return
	 */
	public function findByCourse($course = 0, $limit = 99) {
		$now = time();
		$query = $this->createQuery();
		$query->matching(
			$query->logicalAnd(
				$query->equals('course', $course), 
				$query->greaterThanOrEqual('date', $now)
			)
		);
		$query->setLimit((integer)$limit);
		$posts = $query->execute();
		return $posts;
	}
}

parent-model-new.php

	/**
	 * Returns the events
	 *
	 * @return Tx_Extbase_Persistence_ObjectStorage<Tx_Nboevents_Domain_Model_Event> $events
	 */
	public function getEvents() {
		$eventRepository = t3lib_div::makeInstance('Tx_Nboevents_Domain_Repository_EventRepository');
		return $eventRepository->findByCourse($this->getUid());
	}

	/**
	 * Returns the next event
	 *
	 * @return Tx_Extbase_Persistence_ObjectStorage<Tx_Nboevents_Domain_Model_Event> $events
	 */
	public function getNextevent() {
		$eventRepository = t3lib_div::makeInstance('Tx_Nboevents_Domain_Repository_EventRepository');
		return $eventRepository->findByCourse($this->getUid(), 1);
	}