Symfony3 Related Entity not mapped back to parent on creation - symfony

Question

I have 2 entities Client and Address with a OneToMany relationship.
When I create a new client with an address, it saves both the client and address but does not set the client_id on the address, it is NULL.
I am using fosrestbundle and jmsserializer and sending the data as a json object.
In my controller I have the following:
/**
* #REST\POST("/clients", name="create_client")
*/
public function createClientAction(Request $request)
{
$serializer = $this->get('jms_serializer');
$client = $serializer->deserialize($request->getContent(), 'AppBundle\Entity\Client', 'json');
$em = $this->getDoctrine()->getManager();
$em->persist($client);
$em->flush();
return $this->view($client, 200);
}
Here is a simplified request payload:
{ "name" : "foo", "addresses" : [ { "zip" : "12345" } ]
In my database it creates a new client with name = foo along with an address with zip = 12345, however the field client_id is NULL
My entities are mapped as follows:
//Client.php
...
...
/**
* #ORM\OneToMany(targetEntity="Address", mappedBy="client", cascade={"persist", "remove"})
*/
private $addresses;
//Address.php
...
...
/**
* #ORM\ManyToOne(targetEntity="Client", inversedBy="addresses")
*
*/
private $client;
update
I'm even more confused now, I just realized I do not have any getters/setters in my entities, yet I am able to get / set data.
I am guessing setting has something to do with serializer->deserialize. I have the following in my services:
jms_serializer.object_constructor:
alias: jms_serializer.doctrine_object_constructor
public: false
And getting has something to do with the fosrestbundle. Here is the get route:
/**
* #REST\GET("/clients/{client}", name="get_client")
*/
public function getClientAction(Request $request, Client $client)
{
return $this->view($client, 200);
}

Answer 1

Apparently I needed to merge and not persist the entity.
I updated the route:
$em = $this->getDoctrine()->getManager();
$em->merge($client);
$em->flush();
and the Client entity:
/**
* #ORM\OneToMany(targetEntity="Address", mappedBy="client", cascade={"persist", "remove", "merge"})
*/
private $addresses;
Seems to be working now!