TaskController

/**
     * @Route("/tasks/create", name="task_create")
     * @param Request $request
     * @param Security $security
     * @param FormFactory $formFactory
     * @param Session $session
     * @param RouterInterface $router
     * @return RedirectResponse|Response
     */
    public function createTask(
        Request $request,
        Security $security,
        FormFactory $formFactory,
        Session $session,
        RouterInterface $router
    ): Response {

        $task = new Task();

        $formHandler = new TaskHandler($formFactory->create(TaskType::class, $task), $request);


        // On récupère l 'utilisateur de la session
        $user = $security->getUser();

        //$form = $formFactory->create(TaskType::class, $task);


		if ($formHandler->process()){

            // On attribut le 'username' de la session  à la tache créée
            $task->setUser($user);

            $this->entityManager->persist($task);
            $this->entityManager->flush();

            $session->getFlashBag()->add('success', 'La tâche a été bien été ajoutée.');

            return new RedirectResponse($router->generate('task_list'));
        }

        return new Response($this->twig->render(
            'task/create.html.twig',
            ['form' => $formHandler->getForm()->createView()]
        ));
    }

TaskHandler

<?php
/**
 * Created by Nicolas Dirollo.
 * Date: 04/02/2019
 * Time: 16:22
 * @package     Symfony
 * @author      Nicolas Dirollo
 * @copyright   2019 ND
 * @license     *
 */

namespace AppBundle\Form\Handler;


use Symfony\Component\Form\Form;
use Symfony\Component\HttpFoundation\Request;

class TaskHandler
{
	protected $form;
	protected $request;

	/**
	 * TaskHandler constructor.
	 * @param Form $form
	 * @param Request $request
	 */
	public function __construct(Form $form, Request $request)
	{
		$this->form = $form;
		$this->request = $request;
	}

	/**
	 * @return bool
	 */
	public function process()
	{
		$this->form->handleRequest($this->request);

		if ($this->form->isSubmitted() && $this->form->isValid()) {
			return true;
		}

		return false;
	}

	/**
	 * @return Form
	 */
	public function getForm()
	{
		return $this->form;
	}

	/**
	 *
	 */
	protected function onSuccess()
	{

	}
}