Custom select in a form type in Symfony3

Question

I am creating a select that takes the data of an entity, called category.

The select that I want to develop, would basically be the same that I have developed and working, but with the values ​​I take from the category entity.

namespace AppBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

use Symfony\Component\Form\Extension\Core\Type\TextType;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\Form\Extension\Core\Type\SubmitType;
use BackendBundle\Entity\Categoria;
use BackendBundle\Entity\CategoriaRepository;

class ProductoType extends AbstractType
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
                ->add('nombre', TextType::class, array(
                    'label' => 'Nombre',
                    'required' => 'required',
                    'attr' => array(
                        'class' => 'form-name form-control'
                    )
                ))
                ->add('categoria', ChoiceType::class, array(
                    'choices' => array(
                    'General' => '1',
                    'Coffe' => '2'
                    ),
                    'required'    => false,
                    'empty_data'  => null
                ))
                ->add('Save', SubmitType::class, array(
                    "attr" =>array(
                        "class" => "form-submit btn btn-success"
                    )
                ))
                ;
    }

    /**
     * {@inheritdoc}
     */
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'BackendBundle\Entity\Producto'
        ));
    }

    /**
     * {@inheritdoc}
     */
    public function getBlockPrefix()
    {
        return 'backendbundle_producto';
    }
}

I would add a section like the following, but I get the error Could not load type "entity"

            ->add('categoria', 'entity', array(
                    'class' => 'BackendBundle:Categoria'
                )
            )

The original BBDD is documented in Object of class \BackendBundle\Entity\Categoria could not be converted to string

Answer 1

Firstly if your are using symfony 3 you must use Symfony\Bridge\Doctrine\Form\Type\EntityType and the class should be the class name not the entity name

->add('categoria', 'Symfony\Bridge\Doctrine\Form\Type\EntityType', array(
            'class' => 'BackendBundle\Entity\Categoria'
    )
)

and categoria should look like:

namespace BackendBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Table()
 * @ORM\Entity()
 */
class Categoria
{
    /**
     * @var int
     *
     * @ORM\Id
     * @ORM\Column(name="id", type="integer")
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    protected $id;

    /**
     * @var string
     *
     * @ORM\Column(name="name", type="string")
     */
    protected $name;

    public function __toString()
    {
        return $this->name;
    }
}

Answer 2

'entity' should be EntityType::class, you should use the classname of the EntityType instead of just the 'entity' string

See: https://github.com/symfony/symfony/blob/master/UPGRADE-3.0.md#form