How to clear field value with Symfony2 forms

Question

I\'m writing my own CAPTCHA class and when the form doesn\'t validate, I don\'t want to pre-populate the captcha input with the previous answer, for obvious reasons. I just want

Answer 1

You can pass an incomplete entity to the action called when your control finds form invalid.

public function updateAction(Request $request, $id)
{
    $entity = $this->EM()->getRepository('Bundle:Entity')->find($id);
    if (!$entity) {
        throw $this->createNotFoundException('Unable to find Entity entity.');
    }

    $form = $this->createForm(new RecommendationType()
        ,$entity
        ,array(
            'attr'            => array(
                ,'entity'         => $entity
                )
            )
        );

    $form->bind($request);
    if ($form->isValid()) {
        $this->EM()->persist($entity);
        $this->EM()->flush();

        return $this->redirect($this->generateUrl('entity_show'
            ,array('id' => $id)));
    } else {
        $entity->setCapthca(Null);
    } 

    return $this->render('Bundle:Entity:edit.html.twig'
        ,array(
            'entity'            => $entity
            ,'form'             => $form->createView()
            )
        );
}

The create action would have similar modification.