Updating entity with mappings in Doctrine2 - symfony

Question

I've been doing straight MySQL for a long time and am now trying to do things the ORM way. I have a site where users create designs. The Design table has a field "userId" that maps to User.id. The Design entity has a value, $user, that defines the relationship between entities:
/**
* #ORM\ManyToOne(targetEntity="User")
* #ORM\JoinColumn(name="userId", referencedColumnName="id")
*/
private $user;
It's nice, I can now load a Design entity and get the user's last name with $design->user->lastname.
Now let's say a user creates a new design. I save the entity like:
$design = new Design();
$design->setTitle($_POST['title']);
$design->setUserId($_POST['userId']);
$em = $this->getDoctrine()->getEntityManager();
$em->persist($design);
$em->flush();
When I do this, it fails with the message that userId, which allows no nulls, is null. I thought I might be passing it incorrectly, but when I remove $user from the Design entity it works fine, so I think it's expecting a user object to be passed as well, like:
$design->user = new User($userId)
I don't really want to add a database call just to grab the whole user, when I already know the ID which is all I need. What's the easiest way to handle this?

Answer 1

Hope I have understand your db design that you a user table and design table . Each user may have many designs. right? Then in your entity of design have a field user and its setter(public setUser()) method and a getter method(public getUser()). During the persistance of design entity ,it always expect a user object for User field (not an id) in ORM. In ORM a foreginkey relationship between User and Design it maps through by an object.
So in your case during persistance of design entity
1. Make the user object from userId.
$em = $this->getDoctrine()->getEntityManager();//make your entity manager
$userobj=$em->getRepository('yourBundle:User')->find($userId);
$design = new Design();
$design->setTitle($_POST['title']);
$design->setUser($userobj);
$em->persist($design);
$em->flush();
One Imoprtant thing Make sure that in your design entity that do not have the field userId instead of user. if you have you need to remove the getter and setter method of userid and also edit your yml file or anotation(if you use annotation)