Orm: select entity for update

BaseMapper.php

<?php

use Nextras\Orm\Collection\ICollection;
use Nextras\Orm\Entity\IEntity;
use Nextras\Orm\Mapper\Dbal\Mapper;
use Nextras\Orm\Mapper\Dbal\DbalCollection;

class BaseMapper extends Mapper
{

	/**
	 * @param  DbalCollection $collection
	 * @return IEntity|NULL
	 */
	public function getForUpdate(DbalCollection $collection)
	{
		$builder = $collection->getQueryBuilder();
		$sql = $builder->getQuerySql() . ' LIMIT 1 FOR UPDATE';
		$this->beginTransaction();
		$result = $this->connection->queryArgs($sql, $builder->getQueryParameters())->fetch();
		if ($result) {
			$result = $this->getRepository()->hydrateEntity($result->toArray());
		}
		return $result;
	}

}

example.php

<?php

$collection = $orm->books->findBy([]);
// $collection = $orm->books->findById(...);

$book = $orm->books->getMapper()->getForUpdate($collection);
// $book->title = ''; ...

$this->books->persistAndFlush($book)