CaracoleBundle/Form/Product/ProductToIdTransformer.php

<?php

namespace Lc\CaracoleBundle\Form\Product;

use Doctrine\ORM\EntityManagerInterface;
use Lc\CaracoleBundle\Model\Product\ProductInterface;
use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;

class ProductToIdTransformer implements DataTransformerInterface
{
    private EntityManagerInterface $entityManager;

    public function __construct(EntityManagerInterface $entityManager)
    {
        $this->entityManager = $entityManager;
    }

    public function transform($product)
    {
        if (null === $product) {
            return '';
        }

        return $product->getId();
    }

    public function reverseTransform($productId)
    {
        if (!$productId) {
            return;
        }

        $product = $this->entityManager->getRepository(
                $this->entityManager->getEntityName(ProductInterface::class)
        )->find($productId);

        if (null === $product) {
            throw new TransformationFailedException(
                    sprintf(
                            'An issue with number "%s" does not exist!',
                            $productId
                    )
            );
        }

        return $product;
    }
}