Symfony2 form field constraints validation before Data Transformer - forms

Question

I have created form which requires data transformer, but got myself into single problem: I transform data by exploding string (string should be be exploded to 3 parts), everything works, if I supply correct format string, but otherwise it throws error inside data transformer, because transformation cannot occur if wrong string format is supplied (this is expected behavior).
So the question is is there a way to validate form field for correct string before data transformation? I know that data transformation by default occurs before validation, but maybe there's a way to do it other way around?
I found one solution that might work on this thread: Combine constraints and data transformers ,
but it's looks like rough solution, besides I need to translate validation message, and I would really like to do it using default translation methods for symfony forms (without using translation service)
I thought, and also someone from symfony IRC (Iltar) suggested do it by using events, but I'm not sure how to go about this - how to attach data transformer dynamically to form field? Or maybe there's other way?

Answer 1

It's maybe too late but I eventually manage to do it.
Maybe it will help you.
Here is my FormType:
class PersonType extends AbstractType{
public function buildForm(FormBuilderInterface $builder, array $options){
$builder->add('mother', 'personSelector', array('personEntity' => $options['personEntity']));
}
}
Here is my customField where are validations:
class PersonSelectorType extends AbstractType{
public function buildForm(FormBuilderInterface $builder, array $options){
$transformer = new PersonByFirstnameAndLastnameTransformer($this->entityManager,$options);
$builder->addModelTransformer($transformer);
$builder->addEventListener(FormEvents::PRE_SUBMIT, array($this, 'onPreSubmitForm'));
}
public function onPreSubmitForm(FormEvent $event){
$mother = $event->getData();
$form = $event->getForm();
$options = $form->getConfig()->getOptions();
if (!empty($mother)){
preg_match('#(.*) (.*)#', $mother, $personInformations);
if (count($personInformations) != 3){
$form->addError(new FormError('[Format incorrect] Le format attendu est "Prénom Nom".'));
}else{
$person = $this->entityManager->getRepository($options['personEntity'])->findOneBy(array('firstname' => $personInformations[1],'lastname' =>$personInformations[2]));
if ($person === null) {
$form->addError(new FormError('Il n\'existe pas de person '.$personInformations[1].' '.$personInformations[2].'.'));
}
}
}
}
}
Here is my transformer:
class PersonByFirstnameAndLastnameTransformer implements DataTransformerInterface{
public function reverseTransform($firstnameAndLastname) {
if (empty($firstnameAndLastname)) { return null; }
preg_match('#(.*) (.*)#', $firstnameAndLastname, $personInformations);
$person = $this->entityManager->getRepository($this->options['personEntity'])->findOneBy(array('firstname' =>$personInformations[1],'lastname' =>$personInformations[2]));
if (count($personInformations) == 3){
$person = $this->entityManager->getRepository($this->options['personEntity'])->findOneBy(array('firstname' =>$personInformations[1],'lastname' =>$personInformations[2]));
}
return $person;
}
public function transform($person) {
if ($person === null) { return ''; }
return $person->getFirstname().' '.$person->getLastname();
}
}

Answer 2

Perhaps you could pass the instance of your form to your transformer. If the string doesn't parse correctly, simply add a validation error to the form, like so:
<?php
// src/Acme/MyBundle/Form/DataTransformer/StringTransformer.php
namespace Acme\MyBundle\Form\DataTransformer;
use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;
use Doctrine\Common\Persistence\ObjectManager;
use Acme\MyBundle\Entity\MyEntity;
use Acme\MyBundle\Entity\AnotherEntity;
use Acme\MyBundle\Type\MyEntityType;
class StringTransformer implements DataTransformerInterface
{
/**
* #var MyEntityType
*/
private $form;
/**
* #param ObjectManager $om
*/
public function __construct(MyEntityType $form)
{
$this->form = $form;
}
/**
* Transforms an object (entity) to a string (number).
*
* #param MyEntity|null $entity
* #return string
*/
public function transform($value)
{
// ...
}
/**
* Transforms a string (number) to an object (entity).
*
* #param string $number
*
* #return MyEntity|null
*
* #throws TransformationFailedException if object (entity) is not found.
*/
public function reverseTransform($value)
{
$collection = new ArrayCollection();
try{
$vals = explode(',', $value);
foreach($vals as $v){
$entity = new AnotherEntity();
$entity->setValue($v);
$collection->add($v);
}
} catch(\Exception $e){
$this->form
->get('my_location')
->addError(new FormError('error message'));
}
return $collection;
}
}

Answer 3

but it's looks like rough solution, besides I need to translate validation message, and I would really like to do it using default translation methods for symfony forms (without using translation service)
I know this question is old, but as any answer has been marked yet as the right solution, I share with you another approach.
emottet solution, using a presubmit listener to validate the data before the model transformer has been applied, is a good approach, based on this discussion.
If you want to keep using Symfony validation system for these errors too, you could use Symfony validator service (ValidatorInterface) in your pre-submit listener and pass it the required constraints, for example:
$builder
->add('whatever1', TextType::class)
->add('whatever2', TextType::class)
;
$builder->get('whatever1')
->addEventListener(FormEvents::PRE_SUBMIT, function(FormEvent $event) {
$data = $event->getData();
$form = $event->getForm();
/** #var ConstraintViolationListInterface $errors */
if ($errors = $this->validator->validate($data, new Choice([
'choices' => $allowedChoices,
'message' => 'message.in.validators.locale.xlf'
]))) {
/** #var ConstraintViolationInterface $error */
foreach ($errors as $error) {
$form->addError(new FormError($error->getMessage()));
}
}
})
->addModelTransformer($myTransformer)
;
Kind of redundant, but it works. More info here.