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Sep 9, 2013
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Explained a more simple method of dynamic form handling available since #8827 #2927

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206 changes: 52 additions & 154 deletions cookbook/form/dynamic_form_modification.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -403,31 +403,33 @@ possible choices will depend on each sport. Football will have attack, defense,
goalkeeper etc... Baseball will have a pitcher but will not have goalkeeper. You
will need the correct options to be set in order for validation to pass.

The meetup is passed as an entity hidden field to the form. So we can access each
The meetup is passed as an entity field to the form. So we can access each
sport like this::

// src/Acme/DemoBundle/Form/Type/SportMeetupType.php
namespace Acme\DemoBundle\Form\Type;

// ...

class SportMeetupType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('number_of_people', 'text')
->add('discount_coupon', 'text')
->add('sport', 'entity', array(...))
;
$factory = $builder->getFormFactory();

$builder->addEventListener(
FormEvents::PRE_SET_DATA,
function(FormEvent $event) use($factory){
function(FormEvent $event) {
$form = $event->getForm();

// this would be your entity, i.e. SportMeetup
$data = $event->getData();

$positions = $data->getSport()->getAvailablePositions();

// ... proceed with customizing the form based on available positions
$form->add('position', 'entity', array('choices' => $positions));
}
);
}
Expand All @@ -448,173 +450,69 @@ On a form, we can usually listen to the following events:
* ``BIND``
* ``POST_BIND``

When listening to ``BIND`` and ``POST_BIND``, it's already "too late" to make
changes to the form. Fortunately, ``PRE_BIND`` is perfect for this. There
is, however, a big difference in what ``$event->getData()`` returns for each
of these events. Specifically, in ``PRE_BIND``, ``$event->getData()`` returns
the raw data submitted by the user.
.. versionadded:: 2.2.6

This can be used to get the ``SportMeetup`` id and retrieve it from the database,
given you have a reference to the object manager (if using doctrine). In
the end, you have an event subscriber that listens to two different events,
requires some external services and customizes the form. In such a situation,
it's probably better to define this as a service rather than using an anonymous
function as the event listener callback.

The subscriber would now look like::
The key is to add a ``POST_BIND`` listener to the field your new field is dependent
on. If you add a POST_BIND listener to a form child, and add new children to the parent
from there, the Form component will detect the new field automatically and maps it
to the client data if it is available.

// src/Acme/DemoBundle/Form/EventListener/RegistrationSportListener.php
namespace Acme\DemoBundle\Form\EventListener;
The type would now look like::

use Symfony\Component\Form\FormFactoryInterface;
use Doctrine\ORM\EntityManager;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
// src/Acme/DemoBundle/Form/Type/SportMeetupType.php
namespace Acme\DemoBundle\Form\Type;

class RegistrationSportListener implements EventSubscriberInterface
{
/**
* @var FormFactoryInterface
*/
private $factory;

/**
* @var EntityManager
*/
private $em;

/**
* @param factory FormFactoryInterface
*/
public function __construct(FormFactoryInterface $factory, EntityManager $em)
{
$this->factory = $factory;
$this->em = $em;
}
// ...
Acme\DemoBundle\Entity\Sport;
Symfony\Component\Form\FormInterface;

public static function getSubscribedEvents()
class SportMeetupType extends AbstractType
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missing namespace declarations and use statements.

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I see now that the doc pages are quite inconsistent on this. In this specific page it even changes per example. What exactly is the standard on this?

If I look at this page: http://symfony.com/doc/current/cookbook/form/direct_submit.html, I see that the namespace declaration is always there, but the use statements are simply replaced by // ...

http://symfony.com/doc/current/contributing/documentation/standards.html doesn't say anything about it

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Most of the times, we show all use statements in the first example on a page and fold it on the next examples in the same article. Only new use statements are shown after // ....

{
public function buildForm(FormBuilderInterface $builder, array $options)
{
return array(
FormEvents::PRE_BIND => 'preBind',
FormEvents::PRE_SET_DATA => 'preSetData',
);
}
$builder
->add('sport', 'entity', array(...))
;

/**
* @param event FormEvent
*/
public function preSetData(FormEvent $event)
{
$meetup = $event->getData()->getMeetup();
$formModifier = function(FormInterface $form, Sport $sport) {
$positions = $data->getSport()->getAvailablePositions();

// Before binding the form, the "meetup" will be null
if (null === $meetup) {
return;
$form->add('position', 'entity', array('choices' => $positions));
}

$form = $event->getForm();
$positions = $meetup->getSport()->getPositions();
$builder->addEventListener(
FormEvents::PRE_SET_DATA,
function(FormEvent $event) {
$form = $event->getForm();

$this->customizeForm($form, $positions);
}
// this would be your entity, i.e. SportMeetup
$data = $event->getData();

public function preBind(FormEvent $event)
{
$data = $event->getData();
$id = $data['event'];
$meetup = $this->em
->getRepository('AcmeDemoBundle:SportMeetup')
->find($id);

if ($meetup === null) {
$msg = 'The event %s could not be found for you registration';
throw new \Exception(sprintf($msg, $id));
}
$form = $event->getForm();
$positions = $meetup->getSport()->getPositions();
$formModifier($event->getForm(), $sport);
}
);

$this->customizeForm($form, $positions);
}
$builder->get('meetup')->addEventListener(
FormEvents::POST_BIND,
function(FormEvent $event) use ($formModifier) {
// It's important here to fetch $event->getForm()->getData(), as
// $event->getData() will get you the client data (this is, the ID)
$sport = $event->getForm()->getData();

protected function customizeForm($form, $positions)
{
// ... customize the form according to the positions
$positions = $sport->getAvailablePositions();

// since we've added the listener to the child, we'll have to pass on
// the parent to the callback functions!
$formModifier($event->getForm()->getParent(), $sport);
}
);
}
}

You can see that you need to listen on these two events and have different callbacks
only because in two different scenarios, the data that you can use is given in a
different format. Other than that, this class always performs exactly the same
things on a given form.

Now that you have that setup, register your form and the listener as services:

.. configuration-block::

.. code-block:: yaml

# app/config/config.yml
acme.form.sport_meetup:
class: Acme\SportBundle\Form\Type\SportMeetupType
arguments: [@acme.form.meetup_registration_listener]
tags:
- { name: form.type, alias: acme_meetup_registration }
acme.form.meetup_registration_listener
class: Acme\SportBundle\Form\EventListener\RegistrationSportListener
arguments: [@form.factory, @doctrine.orm.entity_manager]

.. code-block:: xml

<!-- app/config/config.xml -->
<services>
<service id="acme.form.sport_meetup" class="Acme\SportBundle\FormType\SportMeetupType">
<argument type="service" id="acme.form.meetup_registration_listener" />
<tag name="form.type" alias="acme_meetup_registration" />
</service>
<service id="acme.form.meetup_registration_listener" class="Acme\SportBundle\Form\EventListener\RegistrationSportListener">
<argument type="service" id="form.factory" />
<argument type="service" id="doctrine.orm.entity_manager" />
</service>
</services>

.. code-block:: php

// app/config/config.php
$definition = new Definition('Acme\SportBundle\Form\Type\SportMeetupType');
$definition->addTag('form.type', array('alias' => 'acme_meetup_registration'));
$container->setDefinition(
'acme.form.meetup_registration_listener',
$definition,
array('security.context')
);
$definition = new Definition('Acme\SportBundle\Form\EventListener\RegistrationSportListener');
$container->setDefinition(
'acme.form.meetup_registration_listener',
$definition,
array('form.factory', 'doctrine.orm.entity_manager')
);

In this setup, the ``RegistrationSportListener`` will be a constructor argument
to ``SportMeetupType``. You can then register it as an event subscriber on
your form::

private $registrationSportListener;

public function __construct(RegistrationSportListener $registrationSportListener)
{
$this->registrationSportListener = $registrationSportListener;
}

public function buildForm(FormBuilderInterface $builder, array $options)
{
// ...
$builder->addEventSubscriber($this->registrationSportListener);
}

And this should tie everything together. You can now retrieve your form from the
controller, display it to a user, and validate it with the right choice options
set for every possible kind of sport that our users are registering for.
only because in two different scenarios, the data that you can use is available in different events.
Other than that, the listeners always perform exactly the same things on a given form.

One piece that may still be missing is the client-side updating of your form
after the sport is selected. This should be handled by making an AJAX call
Expand Down