Symfony2 Data Transformer receives null - php

Question

My data transformer receives null values in all cases but those with 'multiple'=>true.
For now I'm just trying to var_dump the values.
This is my form:
$entitiesClasses = array(
'AppBundle\Entity\Category' => array( 'label' => 'entity.vehicle.category' ),
'AppBundle\Entity\Specific\ExteriorColor' => array( 'label' => 'entity.specific.exteriorColor' ),
'AppBundle\Entity\Specific\DoorCount' => array( 'label' => 'entity.specific.doorCount' ),
'AppBundle\Entity\Specific\Fuel' => array( 'label' => 'entity.specific.fuel' ),
'AppBundle\Entity\Specific\Gearbox' => array( 'label' => 'entity.specific.gearbox' ),
'AppBundle\Entity\Specific\Climatisation' => array( 'label' => 'entity.specific.climatisation' ),
'AppBundle\Entity\Specific\WheelFormula' => array( 'label' => 'entity.specific.wheelFormula' ),
'AppBundle\Entity\Specific\InteriorColor' => array( 'label' => 'entity.specific.interiorColor' ),
'AppBundle\Entity\Specific\InteriorType' => array( 'label' => 'entity.specific.interiorType' ),
'AppBundle\Entity\Specific\ParkingAssistant' => array( 'label' => 'entity.specific.parkingAssistant', 'multiple' => true ),
'AppBundle\Entity\Feature' => array( 'label' => 'entity.vehicle.features', 'multiple' => true ),
);
$getEntityInputName = function($className) {
$test = preg_split('/\\\/', $className);
return lcfirst(end($test));
};
foreach($entitiesClasses as $className => $options) {
$inputName = $getEntityInputName($className);
isset($options['multiple']) && $options['multiple'] == true? $inputName .= 's' : null;
$formMapper->add(
$formMapper->getFormBuilder()->create($inputName, 'entity',
array_merge(
$options,
array(
'required' => false,
'class' => $className,
'query_builder' => $query_builder,
))
)->addModelTransformer(new EntityTranslationTransformer($this->em))
This is my transformer:
namespace AppBundle\Form\DataTransformer;
use Doctrine\ORM\EntityManager;
use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;
class EntityTranslationTransformer implements DataTransformerInterface
{
/**
* #var EntityManager
*/
private $em;
/**
* #var mixed $entity
*/
private $entity;
/**
* #param EntityManager $em
* #param string $entity
*/
public function __construct(EntityManager $em)
{
$this->em = $em;
}
public function transform($value)
{
if ($value === null) {
return null;
}
return $value;
}
Any idea why this is happening and how to fix it?

Answer 1

if you read here
http://symfony.com/doc/current/cookbook/form/data_transformers.html#creating-the-transformer
transform should change an object into string(an entity to its id), try it as it is in the docs
public function transform($value)
{
if (null === $value) {
return "";
}
return $value->getId();
}
In addition, why do you need a transformer for an entity type field?