Entity form gets null value in Symfony2

Question

I want to add to Model entity one choice from Marka entity . I've problem with data from choices form. Form has got all data inside, but when I send the form i get error:

An exception occurred while executing 'INSERT INTO model (nazwa, idm) VALUES (?, ?)' with params ["a", null]:

SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'idm' cannot be null

When i check source code I see that value is correctly:

   <select id="namefield_idm" name="namefield[idm]" class="form-control"> 
           <option value="1" >Opel</option>
           <option value="2" >Mazda</option> 
           <option value="3" >Ford</option>
    </select>

I don't have any idea whats wrong. My ModelType.php

  <?php
namespace UTPBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Doctrine\ORM\EntityRepository;


    class ModelType extends AbstractType

{

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
    $builder
        ->add('nazwa', 'text', array('label' => 'Nazwa',  'attr' => array(
            'class' => 'form-control')
        ))
        ->add('idm', 'entity', array(
            'label'    => 'Marka',
            'mapped'   => false,
            'class'    => 'UTPBundle:Marka',
            'choice_label' => 'nazwa',
            'attr' => array(
                'class' => 'form-control'
            ),
            'query_builder' => function(EntityRepository $er) {
                return $er->createQueryBuilder('u');
            },
        ))
        ->add('save', 'submit', array('label' => 'Dodaj',  'attr' => array(
            'class' => 'btn btn-success'
        )));
}

public function configureOptions(OptionsResolver $resolver)
{

}

 public function getName()
    {
        return 'namefield';
    }
}
?>

My code from controller looks like:

/**
     * @Route("/model", name="utp_model")
     */
    public function modelAction(Request $request)
    {

        $name = 'Model';


        $model = new Model();
        $marka = new Marka();
        $form = $this->createForm(new ModelType($marka), $model);
        $form->handleRequest($request);

        if ($form->isValid() && $form->isSubmitted()) {
                $em = $this->getDoctrine()->getManager();
                $em->persist($model);
                $em->flush();

        }

        return $this->render('UTPBundle:Default:model.html.twig', array(
            'name' => $name,
            'form' => $form->createView()
        ));
    }

And model entity also:

<?php

namespace UTPBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * Model
 *
 * @ORM\Table()
 * @ORM\Entity
 */
class Model
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @var string
     *
     * @ORM\Column(name="nazwa", type="string", length=255)
     */
    private $nazwa;


    /**
     * @var integer
     *
     * @ORM\Column(name="idm", type="integer")
     */
    private $idm;


    /**
     * Get id
     *
     * @return integer
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set idm
     *
     * @param integer $idm
     *
     * @return Model
     */
    public function setIdm($idm)
    {
        $this->idm = $idm;

        return $this;
    }

    /**
     * Get idm
     *
     * @return string
     */
    public function getIdm()
    {
        return $this->idm;
    }

    /**
     * Set nazwa
     *
     * @param string $nazwa
     *
     * @return Model
     */
    public function setNazwa($nazwa)
    {
        $this->nazwa = $nazwa;

        return $this;
    }

    /**
     * Get nazwa
     *
     * @return string
     */
    public function getNazwa()
    {
        return $this->nazwa;
    }
}

Answer 1

It is not fully clear from your question but I understand that what you want to do is to have a Model entity which will include a Marka field. If that is the case, then first of all, you do not want to store your Marka as an integer within your Model, you want to store it as a Marka object with a (probably) ManyToOne relationship:

/**
 * @ORM\ManyToOne(targetEntity="Marka")
 * @ORM\JoinColumn(name="idm", referencedColumnName="id")
 */
protected $marka;

Doctrine will take care of using an integer to represent this relationship as an integer within your database, using the idm column

Once you have done this, you can then use it in your ModelType form without using 'mapped' => false :

    ->add('marka', 'entity', array(
        'label'    => 'Marka',
        'class'    => 'UTPBundle:Marka',
        'choice_label' => 'nazwa',
        'attr' => array(
            'class' => 'form-control'
        ),
    ))

(Notice that you do not need the query_builder option since your query builder just returns all the objects and the entity field by default already does that.)

And last you just need to modify your controller a bit since you will not need now to create any Marka object:

    $model = new Model();
    $form = $this->createForm(new ModelType(), $model);

Answer 2

In

->add('idm', 'entity', array(
            'label'    => 'Marka',
            'mapped'   => false,
            'class'    => 'UTPBundle:Marka',
            'choice_label' => 'nazwa',
            'attr' => array(
                'class' => 'form-control'
            ),
            'query_builder' => function(EntityRepository $er) {
                return $er->createQueryBuilder('u');
            },
        ))

Remove the line

'mapped'   => false

Mapped false means don't map that property to the underlying object, so it won't be persisted and will then cause your database error.