public function getFirst()
    {
        if (is_array($this->queryResult)) {
            $queryResult = &$this->queryResult;
        } else {
            $query = clone $this->query;
            $query->setLimit(1);
            $queryResult = $this->dataMapper->mapToObjects($this->persistenceManager->getObjectDataByQuery($query));
        }
        return (isset($queryResult[0])) ? $queryResult[0] : null;
    }