Doctrine preUpdate does not actually change entity - php

Question

I am using Doctrine 2.4.6 in my Symfony 2.6.1 project. The problem is that changes made to entity in preUpdate callback are not saved in database. Code follows:
class MyListener {
public function preUpdate(PreUpdateEventArgs $args) {
$entity = $args->getEntity();
$args->setNewValue('name', 'test');
// echo $args->getNewValue('name'); --> prints 'test'
}
}
class DefaultController extends Controller {
/**
* #Route("/commit", name="commit")
*/
public function commitAction(Request $request) {
$content = $request->getContent();
$serializer = $this->get('jms_serializer');
/* #var $serializer \JMS\Serializer\Serializer */
$em = $this->getDoctrine()->getManager();
/* #var $em \Doctrine\Orm\EntityManagerInterface */
$persons = $serializer->deserialize($content, 'ArrayCollection<AppBundle\Entity\Person>', 'json');
/* #var $persons \AppBundle\Entity\Person[] */
foreach($persons as $person) {
$em->merge($person);
}
$em->flush();
return new JsonResponse($serializer->serialize($persons, 'json'));
// Person name is NOT 'test' here.
}
}

Answer 1

The preUpdate doesn't allow you to make changes to your entities. You can only use the computed change-set passed to the event to modify primitive field values. I bet if you check the database you'll see that the Person entities did get updated, you just won't see them in the $persons variable until the next time you manually retrieve them.
What you'll have to do after the flush is retrieve the entities from the database to see their updates values:
$em->flush();
$personIds = array_map(function($person) { return $person->getId(); }, $persons);
$updatedPersons = $em->getRepository('AppBundle:Person')->findById($personIds);
return new JsonResponse($serializer->serialize($updatedPersons, 'json'));