How to customize symfony2 forms upon retrieval? - symfony

Question

I have a case where we create registration for sports events.
The registration contains some fields specific to each sport. Some of which will be named similarly although they will be different for each sport. Example: "favorite position on the field":
For Basketball it would be a choice field between:
Point guard
Shooting guard
etc...
For baseball, it would be the same choice field but with some different choices available:
Pitcher
Infield
Outfield
...
When first creating the form (for display), the sport is passed as part of the data in the registration:
$registration = new Registration;
$registration->setEvent($event);
and $event->getSport(); would return the sport for that event.
So far so good, and adding a listener to the generation of my form, I can set only the fields specific to that sport:
public static function getSubscribedEvents()
{
return [FormEvents::POST_SET_DATA => 'preSetData'];
}
/**
* #param event DataEvent
*/
public function preSetData(DataEvent $event)
{
$form = $event->getForm();
if (null === $event->getData()) {
return;
}
// (The get event here means the real life sports gathering)
$sport = $event->getData()->getEvent()->getSport();
/**
* Then I customize the fields depending on the current sport
*/
}
The problem comes when the user submits this form back. In this case, $event->getData()->getEvent() is null.
The "event" (real life one) is a document_id field in the registration form (using MongoDB here).
If I listen to the ::BIND event instead of ::PRE_SET_DATA, then I can access everything, but it's too late to customize the form as it is already bound. ::PRE_BIND does the same as ::PRE_SET_DATA.
How can I correctly retrieve my Event and Sport Documents here in order to customize my form and validate it appropriately?

Answer 1

Why would you need an event to do such task? You can define the fields in the buildForm() action of the form class. To access the event object simply use $options['data']->getEvent()

Answer 2

So ... Finally found how to do this properly.It requires subscribing to two different events.
First time the form is built, some data is passed to it, therefore, the PRE_SET_DATA event contains that data and everything works fine as explained in the question.
On the moment the form is submitted, it is first created with NO data, therefore the data accessed in PRE_SET_DATA will be null. In this case we skip over the form customization:
public function preSetData(DataEvent $event)
{
$myEvent = $event->getData()->getEvent();
if (null === $myEvent) {
return;
}
$this->customizeForm();
}
This ensures that we don't run into issues when submitting the form and no data is passed, however getData() will return an empty object and not NULL.
Now, when the form is submitted, we will bind it to the data received. That's when we want to interfere. So we'll also subscribe to the PRE_BIND event:
public static function getSubscribedEvents()
{
return [
FormEvents::PRE_BIND => 'preBind',
FormEvents::PRE_SET_DATA => 'preSetData',
];
}
In pre-bind, the data we receive is only an array of values and not an object graph.
But if we injected the object manager in our listener, then we can find our objects and work with them:
public function preBind(DataEvent $event)
{
$data = $event->getData();
$id = $data['event'];
$myEvent = $this->om
->getRepository('Acme\DemoBundle\Document\Event')
->find(new \MongoId($id));
if($myEvent === null){
$msg = 'The event %s could not be found';
throw new \Exception(sprintf($msg, $id));
}
$this->customizeForm();
}