Symfony2 + Ajax: remove form error

Question

I am trying to create entity via Symfony2 and Ajax. When I try to enter existing name, I want to get error under 'Name' textbox. After entering another correct name, I want error message to remove and submit from successfully. My code is not submitting correct data, but keeps adding more error messages.

Controller

    public function createSubmitAction(Request $request){
    $collection = new Collection();
    $user = $this->getUser();
    $form = $this->createForm(
        new CollectionType(),
        $collection
    );


    $form->handleRequest($request);

    $colname = $form["name"]->getData();
    $existing = $this->getDoctrine()->getRepository('CollectionBundle:Collection')->findBy(['name' => $colname, 'user' => $user]);
    if ($existing != NULL) {
        return new JsonResponse(['error' => 'already exists']);
    }

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

        $em = $this->getDoctrine()->getManager();
        $collection->setUser($user);
        $em->persist($collection);
        $em->flush();

        return new JsonResponse([
            'id' => $collection->getId(),
            'name' => $collection->getName()
        ]);
    }
}   

Javascript

  function createInObjectCollection(){
    var $form = $('#create-in-object-form');
    $($form).submit(function(e) {
        e.preventDefault();
        $.ajax({
            type: "POST",
            url: $form.attr('action'),
            data: $form.serialize()
        }).done(function( data ) {
            if (data.error){
                $('<label class="form-error">Collection with such name already exists</label>').insertAfter('#mymini_collectionbundle_collection_name');
                $('#mymini_collectionbundle_collection_name').addClass('error');
            }
            else{
                $("#collection_bundle_add_to_collection option:first-child").after('<option value='+ data.id + '>' + data.name + '</option>');
                $('#createCollectionModal').foundation('reveal', 'close');
            }

        });
    });
}

Answer 1

I have a similar situation. And I use EventListener :

$builder->addEventListener(
        FormEvents::PRE_SET_DATA,
        function (FormEvent $event) {
            $form = $event->getForm();
            $data = $event->getData();

            \\...


        }
    );

And you can use Events like "SUBMIT" and "PRE_SUBMIT".