Symfony2 - How to use a Data Transformer inside EventListeners

Question

• I need to use an Event Listener since I need different things to be displayed in my form whether it is new or an already existing entity. I can manage that.

Answer 1

I have wrote a Form Extension to support this use case without changing type of fields.

1) Create extension class.

namespace AppBundle\Form\Extension\ModelTransformerExtension

use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\Extension\Core\Type\FormType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class ModelTransformerExtension extends AbstractTypeExtension {

    public function getExtendedType() {
        return FormType::class;
    }

    public function buildForm(FormBuilderInterface $builder, array $options) {
        parent::buildForm($builder, $options);

        if (isset($options['model_transformer'])) {
            $builder->addModelTransformer($options['model_transformer']);
        }
    }

    public function configureOptions(OptionsResolver $resolver) {
        parent::configureOptions($resolver);

        $resolver->setDefaults(array('model_transformer' => null));
    }
}

2) Register this extension as an application service.

services:
    app.form.extension.model_transformer:
        class: AppBundle\Form\Extension\ModelTransformerExtension
        tags:
            - { name: form.type_extension, extended_type: Symfony\Component\Form\Extension\Core\Type\FormType }

3) Define model_transformer option to any DataTransformer implement when building the form.

public function buildForm(FormBuilderInterface $builder, array $options) {
    $builder->addEventListener(FormEvents::PRE_SET_DATA, function ($event) {
        $builder = $event->getForm();

        $builder->add('myField', TextType::class, array(
            'model_transformer' => new MyModelTransformer()
        ));
    });
}

This idea can be extended to support addViewTransformer method as well.