Controller.php

<?php

    protected function _editAction(Post $post)
    {
        $em = $this->get('doctrine.orm.default_entity_manager');
        $factory = $this->get('form.factory');
        $form = $factory->create(new PostFormType());
        $form->setData($post);

        if ($this->get('request')->getMethod() === 'POST') {
            $form->bindRequest($this->get('request'));

            if ($form->isValid()) {
                $em->persist($post);
                $em->flush();

                return new RedirectResponse($this->generateUrl('hello_index'));
            }
        }

        return $this->render('MyHelloBundle:Hello:edit.html.twig', array(
            'form' => $form->createView(),
        ));
    }

PostFormType.php

<?php

namespace My\HelloBundle\Form;

use Symfony\Component\Form\FormBuilder;
use Symfony\Component\Form\Type\AbstractType;
use My\HelloBundle\Entity\Comment;

class PostFormType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
            ->add('title')
            ->add('file')
            ->add('content')
            ->add('abstract')
            ->add('enabled')
            ->add('publicationDateStart', 'date')
            ->add('commentsDefaultStatus', 'choice', array(
                'choices' => Comment::getStatusCodes(),
            ))
            // the second parameter, $type, is null because we use auto-creation
            ->add('tags', null, array(
                'expanded' => true,
                'multiple' => true,
            ))
            ->build('author', 'form', array('data_class' => 'My\HelloBundle\Entity\Author'))
                ->add('firstName')
                ->add('lastName')
            ->end();
    }

    public function getDefaultOptions(array $options)
    {
        return array(
            'data_class' => 'My\HelloBundle\Entity\Post',
        );
    }

    public function getName()
    {
        return 'postform';
    }
}

template.html.twig

{% form_theme form _self %}
{{ form_enctype(form) }}
{{ form_widget(form) }}
{{ form_widget(form.firstName) }}

{% for child in form %}
    {{ form_widget(child) }}
{% endfor %}

{{ form_widget(form.firstName, { 'attr': { 'class': 'foobar' } }) }}
{{ form_label(form.firstName, 'My label') }}

@marijn: Unfortunately that's not possible. First of all, your application might provide invalid data of a wrong class or a non-object. Second, in many cases a form doesn't even have an object (think "create" forms), and we still want to be able to guess the types for those. In the above example, what if the $author property of the post is empty?

Well I think the API would be simpler if we would require to inject empty objects in that case...

For example

$form = $factory->create(new PostFormType());
$form->setData(new Post());

Though I'm not sure how that would work out for forms based on arrays...
Those should provide a static method for validation right? So we wouldn't need the class name in that case...

Maybe I'm missing the point here but I'm not convinced of the design requirement of the data_class option...

@marijn: In such a case you would also have to manually prefill the relations of an object, if you use embedded forms.

$post = new Post();
if (!$post->author) {
    $post->author = new Author();
}
if (!$post->author->address) {
    $post->author->address = new Address();
}
$form->setData($post);

You could avoid this mess by setting the empty data option:

class MyEmailType
{
    public function getDefaultOptions()
    {
        return array(
            // can also be a plain object
            'empty_data' => function (FormInterface $form) {
                return new Email(...);
            }
        );
    }
}

But then we have the problem that we need to invoke this closure already when building the form in order to find out the type of the created object, which we can't, because we don't have a FormInterface object yet, only a FormBuilder.

Thanks for clearing that up, it's making sense to me now :-)

How do you handle something kind like EntityChoiceList ? do I have to create my "choices" option array manually ?

@docteurklein Care to elaborate your question?

Sorry if misunderstood :)

I want my form to display a select box corresponding to all the elements of a mongo database collection.
For that, I get an array of Documents and pass it to my choice type via the choices options.

the problem is that the dataTransformer attached to the choice type is a ScalarToChoiceTransformer and it can't handle Object transformation.

FormType:

        $builder->add('frontend_template', 'choice', array(
            'choices' => $this->getTemplateChoices() // this is an array containing Objects
        ))

I finally implemented my own DataTransformer and replaced the Scalar one.

Here is how I did:

$builder->get('frontend_template')->resetClientTransformers();
$builder->get('frontend_template')->appendClientTransformer(new DocumentToChoiceTransformer($this->dm, 'Test\Document\Template'));

Transformer:

<?php

namespace Test\BlockBundle\Form;

use Doctrine\ODM\MongoDB\DocumentManager;

use Symfony\Component\Form\DataTransformerInterface;
use Test\Form\ToIdTransformable;

class DocumentToChoiceTransformer implements DataTransformerInterface
{
    private $dm;
    private $className;

    public function __construct(DocumentManager $dm, $className) 
    {
        $this->dm = $dm;
        $this->className = $className;
    }

    public function transform($value)
    {
        if(null === $value) {

            return '';
        }

        if(is_scalar($value)) {
            return $this->dm->getRepository($this->className)->find($value);
        }

        if( ! $value instanceof ToIdTransformable) {
            throw new \InvalidArgumentException(sprintf('Object must implement "ToIdTransformable" interface'));
        }

        return $value->getId();
    }

    public function reverseTransform($value)
    {
        if(is_scalar($value)) {
            return $this->dm->getRepository($this->className)->find($value);
        }
    }
}

very helpful! thanks

I forgot to say that your domain objects must implement the ToIdTransformable interface:

interface ToIdTransformable
{
    function getId();
}

But I really would like to have the thoughts of @bschussek on this :)