我最近解决了一个类似的问题——Symfony 本身对多态集合没有做出任何让步，但是使用 EventListener 来扩展表单很容易为它们提供支持。
下面是我的 EventListener 的内容，它使用了与 Symfony\Component\Form\Extension\Core\EventListener\ResizeFormListener 类似的方法，事件监听器提供了集合表单类型的正常功能：
namespace Acme\VariedCollectionBundle\EventListener;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Form\FormFactoryInterface;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
class VariedCollectionSubscriber implements EventSubscriberInterface
{
protected $factory;
protected $type;
protected $typeCb;
protected $options;
public function __construct(FormFactoryInterface $factory, $type, $typeCb)
{
$this->factory = $factory;
$this->type = $type;
$this->typeCb = $typeCb;
}
public static function getSubscribedEvents()
{
return array(
FormEvents::PRE_SET_DATA => 'fixChildTypes'
);
}
public function fixChildTypes(FormEvent $event)
{
$form = $event->getForm();
$data = $event->getData();
// Go with defaults if we have no data
if($data === null || '' === $data)
{
return;
}
// It's possible to use array access/addChild, but it's not a part of the interface
// Instead, we have to remove all children and re-add them to maintain the order
$toAdd = array();
foreach($form as $name => $child)
{
// Store our own copy of the original form order, in case any are missing from the data
$toAdd[$name] = $child->getConfig()->getOptions();
$form->remove($name);
}
// Now that the form is empty, build it up again
foreach($toAdd as $name => $origOptions)
{
// Decide whether to use the default form type or some extension
$datum = $data[$name] ?: null;
$type = $this->type;
if($datum)
{
$calculatedType = call_user_func($this->typeCb, $datum);
if($calculatedType)
{
$type = $calculatedType;
}
}
// And recreate the form field
$form->add($this->factory->createNamed($name, $type, null, $origOptions));
}
}
}
使用这种方法的缺点是它要在提交时识别多态实体的类型，您必须在绑定之前将表单上的数据设置为相关实体，否则侦听器无法确定数据的真正类型是。您可以使用 FormTypeGuesser 系统解决这个问题，但这超出了我的解决方案的范围。
同样，虽然使用此系统的集合仍然支持添加/删除行，但它会假定所有新行都是基本类型 - 如果您尝试将它们设置为扩展实体，它会给您一个关于包含的表单的错误额外的字段。
为简单起见，我使用便利类型来封装此功能 - 请参见下面的示例：
namespace Acme\VariedCollectionBundle\Form\Type;
use Acme\VariedCollectionBundle\EventListener\VariedCollectionSubscriber;
use JMS\DiExtraBundle\Annotation\FormType;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\AbstractType;
/**
* @FormType()
*/
class VariedCollectionType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
// Tack on our event subscriber
$builder->addEventSubscriber(new VariedCollectionSubscriber($builder->getFormFactory(), $options['type'], $options['type_cb']));
}
public function getParent()
{
return "collection";
}
public function setDefaultOptions(OptionsResolverInterface $resolver)
{
$resolver->setRequired(array('type_cb'));
}
public function getName()
{
return "varied_collection";
}
}
示例：命名空间 Acme\VariedCollectionBundle\Form；
use Acme\VariedCollectionBundle\Entity\TestModelWithDate;
use Acme\VariedCollectionBundle\Entity\TestModelWithInt;
use JMS\DiExtraBundle\Annotation\FormType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\AbstractType;
/**
* @FormType()
*/
class TestForm extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$typeCb = function($datum) {
if($datum instanceof TestModelWithInt)
{
return "test_with_int_type";
}
elseif($datum instanceof TestModelWithDate)
{
return "test_with_date_type";
}
else
{
return null; // Returning null tells the varied collection to use the default type - can be omitted, but included here for clarity
}
};
$builder->add('demoCollection', 'varied_collection', array('type_cb' => $typeCb, /* Used for determining the per-item type */
'type' => 'test_type', /* Used as a fallback and for prototypes */
'allow_add' => true,
'allow_remove' => true));
}
public function getName()
{
return "test_form";
}
}