Doctrine JoinColumn id is Null - symfony

Question

I'm stuck with my relation.
Here's my entity :
class Orderproduct
/**
* #ORM\OneToMany(targetEntity="ProductBundle\Entity\Product", mappedBy="orderproduct", cascade={"persist"})
*/
private $product;
/**
* #ORM\OneToMany(targetEntity="ProductBundle\Entity\Machining", mappedBy="orderproduct", cascade={"persist"})
*/
private $machining;
And my two others entity :
class Product
/**
* #ORM\ManyToOne(targetEntity="ProductBundle\Entity\Orderproduct", inversedBy="product")
* #ORM\JoinColumn(name="orderproduct_id", referencedColumnName="id", nullable=false)
*/
private $orderproduct;
class Machining
/**
* #ORM\ManyToOne(targetEntity="ProductBundle\Entity\Orderproduct", inversedBy="machining")
* #ORM\JoinColumn(name="orderproduct_id", referencedColumnName="id", nullable=false)
*/
private $orderproduct;
And I've got this error :
SQLSTATE[23000]: Integrity constraint violation: 1048 Le champ 'orderproduct_id' ne peut être vide (null)
Here's my simple add function
public function addOrderproductAction(Request $request)
{
$orderproduct = new Orderproduct();
$formorderproduct = $this->createForm(OrderproductType::class, $orderproduct);
if($formorderproduct->handleRequest($request)->isValid())
{
$em = $this->getDoctrine()->getManager();
$em->persist($orderproduct);
$em->flush();
return $this->redirect($this->generateUrl('product_bundle_listorderproduct'));
}
return $this->render('ProductBundle:Default:neworderproduct.html.twig', array(
'formorderproduct' => $formorderproduct->createView(),
));
}
And i got this with a dump just before the flush :
Any idea ?
Thx for your help!
Edit : After put $product->getOrderproduct($this) and $machining->getOrderproduct($this).
Edit :
I'm changing my model but still have the same problem. So I have a relation between product and machining
Product
/**
* #ORM\OneToMany(targetEntity="ProductBundle\Entity\Machining", mappedBy="product", cascade={"persist"})
*/
private $machining;
Machining
/**
* #ORM\ManyToOne(targetEntity="ProductBundle\Entity\Product", inversedBy="machining")
* #ORM\JoinColumn(name="product_id", referencedColumnName="id")
*/
private $product;
This is Machining table in my Db : product_id is null.
I already try to modify setProduct in Machining but it still the same.

Answer 1

try this:
in Orderproduct' addMachining($machining) method:
$this->machining[] = $machining;
$machining->setOrderproduct($this);
return $this;
the same for the other entity(of course different method name and properties). If this does not work try to persist all entity separately.

Answer 2

So I found a solution :
In the buildForm simply add
'by_reference => false'
Now it's work !