Symfony how to validate EntityType field

Question

I have this EntityType field on my UserType's form:

public function buildForm(FormBuilderInterface $builder, array $options)
{
        $builder->add('country', EntityType::class, array(
             'class' => Country::class,
             'choice_label' => 'nicename'
        ));
}

How can i use validation constraints to validate this type of field in the way that user can only select a value in the range of all rows of country's table? I think that I should use Choice constraint with callback, and call the getAllCountries function inside my CountryRepository class. So what's the best way to manage this scenario?

Somethins like this:

// UserEntity.php

class User {

     /**
     * @Assert\Choice(callback="App\Repository\CountryRepository", "getAllCountries")
     * @ORM\ManyToOne(targetEntity="App\Entity\Country", inversedBy="users")
     */
    protected $country;
}

But CountryRepository is not a static function!!

Answer 1

Entity field doesn't allow to select invalid value (if you have invalid value it would't find the entity -> wouldn't be able to send form). This is as well behaviour of choice type.

But for callback, there is special callback constraint - https://symfony.com/doc/current/reference/constraints/Callback.html which can be used to call constraint function.