Symfony: How to get related entity in form listener?

Question

symfony

So, there are three entities: Country, Region, City
City is associated with the region, Region with the country (many to one)
I create a form class for the City entity: there will be 2 selects (Country and Region) and a text field for the City name.
Selects:
- Region is a mapped field for the entity parameter City
- Country - non-mapped field, added to the form using the Event
Listener
, when re-editing the City - region is selected in the selectbox.
But I cannot get the Country by Region in any way (although the region is tied to the country). That is, I pull Region:getCountry() in the listener - and it is always NULL.
Although in other places of the application this method works out with a bang, there are no problems.
Here is a listing of entities, or rather their relationships:

class Country
    {
        /**
         * @ORM\OneToMany(targetEntity="OQ\ReferenceBundle\Entity\Region", mappedBy="country")
         */
        protected $regions;
    }


    class Region
    {
        /**
         * @ORM\ManyToOne(targetEntity="OQ\ReferenceBundle\Entity\Country", inversedBy="regions")
         * @ORM\JoinColumn(name="country_id", referencedColumnName="id", nullable=false)
         */
        protected $country;
    
        /**
         * @ORM\OneToMany(targetEntity="OQ\ReferenceBundle\Entity\City", mappedBy="region")
         */
        protected $cities;
    }

    class City
    {
        /**
         * @ORM\ManyToOne(targetEntity="OQ\ReferenceBundle\Entity\Region", inversedBy="cities")
         * @ORM\JoinColumn(name="region_id", referencedColumnName="id", nullable=false)
         */
        protected $region;
    }

And here is the listing of the form class:

class CityType extends AbstractType
    {
        /**
         * {@inheritdoc}
         */
        public function buildForm(FormBuilderInterface $builder, array $options)
        {
    
            $builder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
    
                if ($event->getData() instanceof City) {
                    $form = $event->getForm();
                    $data = $event->getData();
                    $region = $data->getRegion(); // California
                    $country = $region->getCountry(); // NULL, but California is related to USA
                    
                    $form->add(
                        'country',
                        'translatable_entity',
                        [
                            'mapped' => false,
                            'label' => 'oq.reference.country.entity_label',
                            'class' => 'OQReferenceBundle:Country',
                            'property' => 'name',
                            'required' => true,
                            'empty_value' => 'oq.reference.country.choose',
                            'property_path' => false,
                            'data' => $country
                        ]
                    );
                }
            });
    
            $builder
                ->add(
                    'name',
                    'text',
                    [
                        'required' => true,
                        'label' => 'oq.reference.city.name.label'
                    ]
                )->add(
                    'region',
                    'translatable_entity',
                    array(
                        'label' => 'oq.reference.region.entity_label',
                        'class' => 'OQReferenceBundle:Region',
                        'property' => 'name',
                        'required' => true,
                        'empty_value' => 'oq.reference.region.choose'
                    )
                );
        }
    
        ...
    
    }

It is in this piece that the suction of the associated Country occurs (or rather does not occur)

$builder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
        
                    if ($event->getData() instanceof City) {
                        $form = $event->getForm();
                        $data = $event->getData();
                        $region = $data->getRegion(); // California
                        $country = $region->getCountry(); // NULL, but California is related to USA
                        
                        ...

Answer 1

When creating a city in this form, the country will always be null.
When editing, must be an entity.
The region in the listener is a proxy object and is not initialized.
A strange form of city selection.
When creating a city, bypassing the region, I can select a country by creating the Moscow region in any country.
Usually they do the opposite, go down from top to bottom.