Flush One-To-Many, Self-referencing - php

Question

I have self-referencing one-to-many relationship (I did it in accordance with Documentation: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/association-mapping.html#one-to-many-self-referencing )
Now I want flush new element to Entity, but how can I use ID of new flush element to put it in referencing place?
I try with:
$newProject->setSubprojectId($newProject);
and with:
$newProject->setSubprojectId($newProject->getId());
but I think that it's impossible to get ID of object before flush it. I'm right?
My code looks like:
/**
* #Route("/project/manage", name="project_edit");
*/
public function registerAction(Request $request)
{
$user = $this->get('security.token_storage')->getToken()->getUser();
$newProject = new Project();
$newProject->setIsActive(1);
$newProject->setOwner($user);
$newProject->setCreateDate( new \DateTime() );
$newProject->setSubprojectId($newProject);
$formProject = $this->createForm(AddProject::class, $newProject);
$formProject->handleRequest($request);
if($formProject->isSubmitted() && $formProject->isValid()){
$em = $this->getDoctrine()->getManager();
$em->persist($newProject);
$em->flush();
return $this->render('xxx/projectEdit.html.twig', array(
'form' => $formProject->createView(),
));
}
return $this->render('xxx/projectEdit.html.twig', array(
'form' => $formProject->createView(),
));
}
EDIT
I found different solutions but the question remains valid - it's possible to get this id before flush or to flush id for two columns in the same time?

Answer 1

You could try setting cascade persist, however why not just do:
$em = $this->getDoctrine()->getManager();
$em->persist($newProject);
$em->flush();
$newProject->setSubProject($newProject); // *why* do you want to do this?
$em->persist($newProject);
$em->flush();
You shouldn't need to mess about with setting ids directly. You should be able to accomplish this by using the setter on your object and doctrine should take care of the ids for you.