Why is a form not being submitted in Symfony 3?

Question

symfony

The form is rendered to the page through the Twig tag

{{ render(controller('AppBundle:Device:formSelectedDevice')) }}

Form code:

<?php

namespace AppBundle\Form;

use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class SelectedDeviceType extends EntityBaseType
{
    /**
     * @param FormBuilderInterface $builder
     * @param array $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('device', EntityType::class, array(
                'label' => 'Выберите прибор',
                'class' => 'AppBundle\Entity\Device',
                'empty_data' => $options['data']['device']
            ))
        ;
    }
    
    /**
     * @param OptionsResolver $resolver
     */
    public function configureOptions(OptionsResolver $resolver)
    {
    }
}

Action code in controller:

public function formSelectedDeviceAction(Request $request)
    {
        $selectedDeviceId = $request->getSession()->get('device') ?: 1;

        $data = array();
        $data['device'] = $this->service->getEntity($selectedDeviceId);

        $form = $this->createForm(SelectedDeviceType::class, $data);
        $form->handleRequest($request);

        if($form->isValid()) {
            dump($form->getData());
            $request->getSession()->set('device', $form->getData()['device']->getId());
        }

        return $this->render('AppBundle:Device/block:selected-device.html.twig', array(
            'form' => $form->createView()
        ));
    }

The isValid condition is not met when the form is submitted,
The isSubmitted condition is not met when the form is submitted.
Tell me, what's the problem?

Answer 1

The isSubmitted condition is not met when the form is submitted.

It looks like you are submitting the form with a GET, but $form->handleRequest($request);waiting for a POST request.
Or specify the method explicitly

$this->createForm(SelectedDeviceType::class, $data, array(
    'method' => 'GET'
));

or send POST
+ the form is rendered via a sub-request, then the submission goes to the current page:

$this->createForm(SelectedDeviceType::class, $data, array(
    'action' => $this->generateUrl('form_submit_route');
));

Answer 2

isValid condition fails on form submission,

Get a list of errors from the form and see what's wrong.
Did you add a submit button to the form?