NullableBooleanType for Symfony REST API

nullable_boolean_type.php

<?php

namespace App\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\Form\CallbackTransformer;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class NullableBooleanType extends AbstractType
	{
	public function configureOptions(OptionsResolver $resolver): void
		{
		$resolver->setDefaults([
			'required' => false,
			'choices' => [-1,0,1]
		]);
		}

	public function buildForm(FormBuilderInterface $builder, array $options): void
		{
		$builder
			->addModelTransformer(new CallbackTransformer(
				static function($orig) {
					if ($orig === null) {
						return 0;
					}
					return $orig ? 1 : -1;
				},
				static function($submitted) {
					if ($submitted === null || $submitted === 0) {
						return null;
					}
					return $submitted === 1;
				}
			));
		}

	public function getParent(): string
		{
		return ChoiceType::class;
		}
	}