Why do some values ​​go to null after $form->handleRequest($request)?

Question

symfony

Hello. I'm recently working with Symfony 4 for this reason and there are a lot of things I don't understand. Faced such a situation that when creating a new record (I work not through Entity but through DTO), some parameters were set to null.

dump($request->get('hotel_form_builder')):
"countryId" => "189"
  "cityId" => "425754"
dump($form->getData()):
  +countryId: null
  +cityId: null

To be more specific, these are 2 parameters (`countryId` and `cityId`). For these two fields, their own type Select2Type was "written":

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\FormView;
use Symfony\Component\Form\FormInterface;

class Select2Type extends AbstractType {
    public function buildView(FormView $view, FormInterface $form, array $options)
    {
        $attr = $view->vars['attr'];
        $class = isset($attr['class']) ? $attr['class'].' ' : '';
        $class .= 'select2';
        $attr['class'] = $class;
        $attr['data-autocomplete-url'] = $attr['data-autocomplete-url'];
        $view->vars['attr'] = $attr;
    }
    public function getParent() {
        return ChoiceType::class;
    }
    public function configureOptions(OptionsResolver $resolver) {
        $resolver->setDefaults([
            'attr' => [
                'class' => 'form-control select2',
                'data-autocomplete-url' => ''
            ]
        ]);
    }
}

I pass the data via url in the form {id: id, text: 'text'}. There is a high probability that I incorrectly described or wrote something.
This is part of the code from buildForm:

...
            ->add('countryId', Select2Type::class, [
                'label'              => 'hotel.field.countryId',
                'translation_domain' => 'hotel_inventory',
                'required'           => true,
                'attr'               => [
                    'data-autocomplete-url' => $router->generate('hotel_country'),
                    'class'                 => 'form-control select2SearchCountry',
                ]
            ])
            ->add('cityId', Select2Type::class, [
                'label'              => 'hotel.field.cityId',
                'translation_domain' => 'hotel_inventory',
                'required'           => true,
                'attr'               => [
                    'data-autocomplete-url' => $router->generate('hotel_city'),
                    'class'                 => 'form-control select2SearchCity',
                ]
            ])
...

I would be grateful for help. If you have any ideas or questions please ask. Suddenly together we will understand where the problem is.

Answer 1

Specify default values ​​in the entity, for example:

/**
     * @var bool
     *
     * @ORM\Column(name="active", type="boolean")
     */
    private $active = true;