How to setup a data transformer in Symfony to reus

Question

I'm working on an article editor in Symfony with built-in tagging capability:

The controller

class MainController extends Controller
{
    public function indexAction(Request $request, $id)
    {
        $em = $this->getDoctrine()->getManager();

        // $article = ...

        $form = $this->createForm(new ArticleType(), $article);
        $form->handleRequest($request);

        if ($form->isValid()) {
            $em->persist($article);
            $em->flush();
            return $this->redirect($this->generateUrl('acme_edit_success'));
        }

        return $this->render('AcmeBundle:Main:index.html.twig', array(
            'form' => $form->createView()
        ));

    }
}

The forms

The tag form is registered as a service with the @Doctrine argument, so I can use the entity manager inside the class. The tag form is embed inside the article form.

ArticleType.php

class ArticleType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('content')
            ->add('tags', 'collection', array(
                'type' => 'acme_bundle_tagtype',
                'allow_add' => true,
                'allow_delete' => true,
                'by_reference' => false
            ))
            ->add('save', 'submit')
        ;
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'Acme\Bundle\Entity\Article',
            'cascade_validation' => true
        ));
    }

    public function getName()
    {
        return 'acme_bundle_articletype';
    }
}

TagType.php

class TagType extends AbstractType
{
    private $entityManager;

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $transformer = new TagTransformer($this->entityManager);

        $builder->add(
            $builder->create('name')
                ->addModelTransformer($transformer)
        );
    }

    function __construct(\Doctrine\Bundle\DoctrineBundle\Registry $doctrine) {
        $this->entityManager = $doctrine->getManager();
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'Acme\Bundle\Entity\Tag'
        ));
    }

    public function getName()
    {
        return 'acme_bundle_tagtype';
    }
}

The data transformer

I created this data transformer to check if the given tag already exists and then transform the tag object to the one that already exists in the database:

class TagTransformer implements DataTransformerInterface
{
    /**
     * @var ObjectManager
     */
    private $om;

    /**
     * @param ObjectManager $om
     */
    public function __construct(ObjectManager $om)
    {
        $this->om = $om;
    }

    public function transform($tag)
    {
        if (null === $tag) {
            return '';
        }

        return $tag;
    }

    public function reverseTransform($name)
    {
        if (!$name)
            return null;

        $tag = $this->om
            ->getRepository('AcmeBundle:Tag')
            ->findOneByName($name)
        ;

        if (!$tag) {
            $tag = new Tag();
            $tag->setName($name);
        }

        return $tag;
    }
}

When I try to save an article with an already existing tag, the reverseTransform() function successfully returns the original tag objects, but the DBAL converts the object back to a string by its __toString() method, and Doctrine still initiates an INSERT query instead of UPDATE, so I get the next error:

An exception occurred while executing 'INSERT INTO Tag (name) VALUES (?)' with params [{}]:

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'An Existing Tag' for key 'UNIQ_0123456789ABCDE'

How can I fix this? When I enter a tag name that's already in use, I want Symfony to use the same tag in the article-tag relationship. The entity classes appear in my previous question about how to avoid duplicate entries in a many-to-many relationship with Doctrine.

Answer 1

There's one mistake in your transformer. Instead of checking if name is null you should verify if a tag was returned:

    if (!$tag) {
        $tag = new Tag();
        $tag->setName($name);
    }

You also don't need to persist the tag since by default doctrine will cascade persist all the related entities.

Full method:

public function reverseTransform($name)
{
    if (!$name) {
        return null;
    }

    $tag = $this->om
        ->getRepository('AcmeBundle:Tag')
        ->findOneByName($name)
    ;

    if (!$tag) {
        $tag = new Tag();
        $tag->setName($name);
    }

    return $tag;
}