Controller/FormWebsiteController.php
public function formAction(StructureInterface $structure, $preview = false, $partial = false)
    {
        /** @var Request $request */
        $request = $this->get('request_stack')->getCurrentRequest();

        // get attributes
        $attributes = $this->getAttributes([], $structure, $preview);

        $template = $structure->getKey();

        $typeClass = $this->getTypeClass($template);
        /** @var AbstractType $type */
        $type = $this->get('form.registry')->getType($typeClass)->getInnerType();
        $type->setAttributes($attributes);

        $this->form = $this->get('form.factory')->create($typeClass);
        $this->form->handleRequest($request);

        if ($this->form->isSubmitted()
            && $this->form->isValid()
            && $response = $this->handleFormSubmit($request, $type, $attributes)
        ) {
            // success form submit

            return $response;
        }

        return parent::indexAction($structure, $preview, $partial);
    }
public function formAction(StructureInterface $structure, $preview = false, $partial = false)
    {
        /** @var Request $request */
        $request = $this->get('request_stack')->getCurrentRequest();

        // get attributes
        $attributes = $this->getAttributes([], $structure, $preview);

        $template = $structure->getKey();

        $typeClass = $this->getTypeClass($template);
        /** @var AbstractType $type */
        $type = $this->get('form.registry')->getType($typeClass)->getInnerType();
        $type->setAttributes($attributes);

        $this->form = $this->get('form.factory')->create($typeClass);
        $this->form->handleRequest($request);

        if ($this->form->isSubmitted()
            && $this->form->isValid()
            && $response = $this->handleFormSubmit($request, $type, $attributes)
        ) {
            // success form submit

            return $response;
        }

        return parent::indexAction($structure, $preview, $partial);
    }
Form action.

@param StructureInterface $structure
@param bool $preview
@param bool $partial

@return JsonResponse|RedirectResponse|Response