Symfony2 collection of Entities – how to add/remove association with existing entities?

I’ve come to the same conclusion that there’s something wrong with the Form component and can’t see an easy way to fix it. However, I’ve come up with a slightly less cumbersome workaround solution that is completely generic; it doesn’t have any hard-coded knowledge of entities/attributes so will fix any collection it comes across:

Simpler, generic workaround method

This doesn’t require you to make any changes to your entity.

use Doctrine\Common\Collections\Collection;
use Symfony\Component\Form\Form;

# In your controller. Or possibly defined within a service if used in many controllers

/**
 * Ensure that any removed items collections actually get removed
 *
 * @param \Symfony\Component\Form\Form $form
 */
protected function cleanupCollections(Form $form)
{
    $children = $form->getChildren();

    foreach ($children as $childForm) {
        $data = $childForm->getData();
        if ($data instanceof Collection) {

            // Get the child form objects and compare the data of each child against the object's current collection
            $proxies = $childForm->getChildren();
            foreach ($proxies as $proxy) {
                $entity = $proxy->getData();
                if (!$data->contains($entity)) {

                    // Entity has been removed from the collection
                    // DELETE THE ENTITY HERE

                    // e.g. doctrine:
                    // $em = $this->getDoctrine()->getEntityManager();
                    // $em->remove($entity);

                }
            }
        }
    }
}

Call the new cleanupCollections() method before persisting

# in your controller action...

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

        // 'Clean' all collections within the form before persisting
        $this->cleanupCollections($form);

        $em->persist($user);
        $em->flush();

        // further actions. return response...
    }
}