Using a Data Transformer in Symfony to handle duplicate tags

This is Part 3 in a series on setting up Tags in a ManyToMany association with an Entity in Symfony. You can read the previous two articles here:

In the last article, I talked about the problem of duplicate Tags being added when creating a new Product. Here, I will show one way to handle that using a Data Transformer.

First, we will create the data transformer:

// src/AppBundle/Form/DataTransformer/TagsToCollectionTransformer.php

namespace AppBundle\Form\DataTransformer;

use Doctrine\Common\Persistence\ObjectManager;
use Symfony\Component\Form\DataTransformerInterface;
use Doctrine\Common\Collections\ArrayCollection;

class TagsToCollectionTransformer implements DataTransformerInterface
{

    private $manager;

    public function __construct(ObjectManager $manager)
    {
        $this->manager = $manager;
    }

    public function transform($tags)
    {
        return $tags;
    }

    public function reverseTransform($tags)
    {
        $tagCollection = new ArrayCollection();

        $tagsRepository = $this->manager
                ->getRepository('AppBundle:Tag');

        foreach ($tags as $tag) {

            $tagInRepo = $tagsRepository->findOneByName($tag->getName());

            if ($tagInRepo !== null) {
                // Add tag from repository if found
                $tagCollection->add($tagInRepo);
            }
            else {
                // Otherwise add new tag
                $tagCollection->add($tag);
            }
        }

        return $tagCollection;
    }

}

// src/AppBundle/Form/DataTransformer/TagsToCollectionTransformer.php

namespace AppBundle\Form\DataTransformer;

use Doctrine\Common\Persistence\ObjectManager;

use Symfony\Component\Form\DataTransformerInterface;

use Doctrine\Common\Collections\ArrayCollection;

class TagsToCollectionTransformer implements DataTransformerInterface

{

private $manager;

public function __construct(ObjectManager $manager)

{

$this->manager = $manager;

}

public function transform($tags)

{

return $tags;

}

public function reverseTransform($tags)

{

$tagCollection = new ArrayCollection();

$tagsRepository = $this->manager

->getRepository('AppBundle:Tag');

foreach ($tags as $tag) {

$tagInRepo = $tagsRepository->findOneByName($tag->getName());

if ($tagInRepo !== null) {

// Add tag from repository if found

$tagCollection->add($tagInRepo);

}

else {

// Otherwise add new tag

$tagCollection->add($tag);

}

return $tagCollection;

}

Your data transformer implements the DataTransformerInterface, which requires these two methods:

public function transform($value);

public function reverseTransform($value);

public function transform($value);

public function reverseTransform($value);

transform allows you to alter the data going to your form. We don’t need to change this, so can just return the tags as is.

reverseTransform allows you to alter the data submitted by your form. This is where we want to make our changes.

In the constructor, the ObjectManager is injected for checking a Tag’s existence in the database.

In the reverseTransform method, an empty ArrayCollection is created to store all tags we’ll be returning. For each submitted Tag, it checks for its presence in the Tag repository. If present, we replace the form submitted Tag with the one already present in the Tag repository. If not, then we allow the new form submitted Tag into the $tagCollection .

Finally, the $tagCollection is returned.

You can do any other filtering you like there. But for the purposes of this tutorial, we’ll keep it simple like that.

The next thing we need to do is make a few changes to our ProductType:

// src/AppBundle/Form/Type/ProductType.php

namespace AppBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\Extension\Core\Type\CollectionType;
use Doctrine\Common\Persistence\ObjectManager;
use AppBundle\Form\DataTransformer\TagsToCollectionTransformer;

class ProductType extends AbstractType
{

    private $manager;

    public function __construct(ObjectManager $manager)
    {
        $this->manager = $manager;
    }

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
                ->add('name')
                ->add('tags', CollectionType::class, array(
                    'entry_type' => TagType::class,
                    'allow_add' => true,
                    'allow_delete' => true,
                    'required' => false
                ));
        
        // Data Transformer
        $builder
                ->get('tags')
                ->addModelTransformer(new TagsToCollectionTransformer($this->manager));
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'AppBundle\Entity\Product',
        ));
    }

}

// src/AppBundle/Form/Type/ProductType.php

namespace AppBundle\Form\Type;

use Symfony\Component\Form\AbstractType;

use Symfony\Component\Form\FormBuilderInterface;

use Symfony\Component\OptionsResolver\OptionsResolver;

use Symfony\Component\Form\Extension\Core\Type\CollectionType;

use Doctrine\Common\Persistence\ObjectManager;

use AppBundle\Form\DataTransformer\TagsToCollectionTransformer;

class ProductType extends AbstractType

{

private $manager;

public function __construct(ObjectManager $manager)

{

$this->manager = $manager;

}

public function buildForm(FormBuilderInterface $builder, array $options)

{

$builder

->add('name')

->add('tags', CollectionType::class, array(

'entry_type' => TagType::class,

'allow_add' => true,

'allow_delete' => true,

'required' => false

));

// Data Transformer

$builder

->get('tags')

->addModelTransformer(new TagsToCollectionTransformer($this->manager));

}

public function configureOptions(OptionsResolver $resolver)

{

$resolver->setDefaults(array(

'data_class' => 'AppBundle\Entity\Product',

));

}

We’ll be using the ObjectManager and our newly created TagsToCollectionTransformer :

use Doctrine\Common\Persistence\ObjectManager;
use AppBundle\Form\DataTransformer\TagsToCollectionTransformer;

1 2	use Doctrine\Common\Persistence\ObjectManager; use AppBundle\Form\DataTransformer\TagsToCollectionTransformer;

The ObjectManager is injected in the constructor. (We’ll create a service for our ProductType class later)

We also get 'tags' from our form builder, add our transformer to it using the addModelTransformer method, and pass in the ObjectManager dependency to our TagsToCollectionTransformer .

Finally, we create a service for our ProductType class which injects the ObjectManager dependency to it:

# app/config/services.yml

services:
    app.form.type.product:
        class: AppBundle\Form\Type\ProductType
        arguments: ["@doctrine.orm.entity_manager"]
        tags:
            - { name: form.type }

# app/config/services.yml

services:

app.form.type.product:

class: AppBundle\Form\Type\ProductType

arguments: ["@doctrine.orm.entity_manager"]

tags:

- { name: form.type }

Our form is now ready to roll.

Let’s create a controller for submitting new Products:

// src/AppBundle/Controller/ProductController.php

namespace AppBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Component\HttpFoundation\Request;
use AppBundle\Entity\Product;
use AppBundle\Form\Type\ProductType;

class ProductController extends Controller 
{
    /**
     * @Route("/new/product", name="new_product")
     */
    public function newProductAction(Request $request)
    {
        $product = new Product();
        
        $form = $this->createForm(ProductType::class, $product);
        $form->handleRequest($request);
        
        if ($form->isSubmitted() && $form->isValid()) {
            $em = $this->getDoctrine()->getManager();
            $em->persist($product);
            $em->flush();
        }
        
        return $this->render('product/submitProduct.html.twig', array(
            'form' => $form->createView()
        ));
    }
}

// src/AppBundle/Controller/ProductController.php

namespace AppBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

use Symfony\Component\HttpFoundation\Request;

use AppBundle\Entity\Product;

use AppBundle\Form\Type\ProductType;

class ProductController extends Controller

{

/**

* @Route("/new/product", name="new_product")

public function newProductAction(Request $request)

{

$product = new Product();

$form = $this->createForm(ProductType::class, $product);

$form->handleRequest($request);

if ($form->isSubmitted() && $form->isValid()) {

$em = $this->getDoctrine()->getManager();

$em->persist($product);

$em->flush();

}

return $this->render('product/submitProduct.html.twig', array(

'form' => $form->createView()

));

}

This should be pretty self-explanatory if you’re familiar with controllers, routes, form submissions, and persisting objects to the database in Symfony. Basically we just create our form with a new Product object, and have the form handle the Request. If a form was submitted, and is valid, we persist the Product to the database. Finally, we render the submitProduct template which will be created later.

Note that while it’s not actually required to check $form->isSubmitted() , it is recommended per the Symfony best practices on form submissions for readability:

Second, we recommend using $form->isSubmitted() in the if statement for clarity. This isn’t technically needed, since isValid() first calls isSubmitted(). But without this, the flow doesn’t read well as it looks like the form is always processed (even on the GET request).

The last thing to do is create the Twig template submitProduct.html.twig which will display our form. Since we’ll be adding and removing Tags from Products, we’ll need some JavaScript to add/remove our tag.name inputs for us. You could accomplish this using the example in the Symfony documentation, but in the next article, we’ll be using the jQuery Tag-it plugin instead.

Next article: How to use jQuery Tag-it plugin with a Symfony form