Display empty form collection item in Symfony without using javascript - symfony

Question

I'm trying to display a form with a collection. The collection should display an empty sub-form. Due to the projects nature I can't rely on JavaScript to do so.
Googling didn't help and I does not seem to work by adding an empty entity to the collection field.
What I have so far:
public function indexAction($id)
{
$em = $this->getDoctrine()->getManager();
$event = $em->getRepository('EventBundle:EventDynamicForm')->find($id);
$entity = new Booking();
$entity->addParticipant( new Participant() );
$form = $this->createForm(new BookingType(), $entity);
return array(
'event' => $event,
'edit_form' => $form->createView()
);
}
In BookingType.php buildForm()
$builder
->add('Participants', 'collection')
In the Twig template
{{ form_row(edit_form.Participants.0.companyName) }}
If I put the line $entity->addParticipant( new Participant() ); in indexAction() I get an error saying:
The form's view data is expected to be of type scalar, array or an
instance of \ArrayAccess, but is an instance of class
Yanic\EventBundle\Entity\Participant. You can avoid this error by
setting the "data_class" option to
"Yanic\EventBundle\Entity\Participant" or by adding a view transformer
that transforms an instance of class
Yanic\EventBundle\Entity\Participant to scalar, array or an instance
of \ArrayAccess.
If I delete the said line Twig complains:
Method "0" for object "Symfony\Component\Form\FormView" does not exist in
/Applications/MAMP/htdocs/symfony-standard-2.1/src/Yanic/EventBundle/Resources/views/Booking/index.html.twig
at line 27
EDIT: The addParticipant is the default methos generated by the doctrine:generate:entities command
/**
* Add Participants
*
* #param \Yanic\EventBundle\Entity\Participant $participants
* #return Booking
*/
public function addParticipant(\Yanic\EventBundle\Entity\Participant $participants)
{
$this->Participants[] = $participants;
return $this;
}
I'm sure that I'm doing something wrong, but can't find the clue :-(

Answer 1

I guess you are a bit lost on Symfony2 form collection, though I think you already read http://symfony.com/doc/current/cookbook/form/form_collections.html.
Here I will just emphasize the doc, help other SO readers, and exercise myself a bit on answering question.. :)
First, you must have at least two entities. In your case, Booking and Participant. In Booking entity, add the following. Because you use Doctrine, Participant must be wrapped in ArrayCollection.
use Doctrine\Common\Collections\ArrayCollection;
class Booking() {
// ...
protected $participants;
public function __construct()
{
$this->participants = new ArrayCollection();
}
public function getParticipants()
{
return $this->participants;
}
public function setParticipants(ArrayCollection $participants)
{
$this->participants = $participants;
}
}
Second, your Participant entity could be anything. Just for example:
class Participant
{
private $name;
public function setName($name) {
$this->name = $name;
return $this;
}
public function getName() {
return $this->name;
}
}
Third, your BookingType should contain collection of ParticipantType, something like this:
// ...
$builder->add('participants', 'collection', array('type' => new ParticipantType()));
Fourth, the ParticipantType is straightforward. According to my example before:
// ...
$builder->add('name', 'text', array('required' => true));
Last, in BookingController, add the necessary amount of Participant to create a collection.
// ...
$entity = new Booking();
$participant1 = new Participant();
$participant1->name = 'participant1';
$entity->getParticipants()->add($participant1); // add entry to ArrayCollection
$participant2 = new Participant();
$participant2->name = 'participant2';
$entity->getParticipants()->add($participant2); // add entry to ArrayCollection

Answer 2

think you have to add here the type:
->add('Participants', 'collection', array('type' => 'YourParticipantType'));
Could you also paste in here the declaration of your addParticipant function from the model? Seems that there's something fishy too.