I have a form like below:

```php
class ItemType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            // ...
            ->add('tags','text',array(
                'required' => false,
                'attr' => array('name' => 'tags'),
                'mapped' => false))
        ;
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'MyBundle\ItemBundle\Entity\Item',
            'cascade_validation' => true,
        ));
    }
}

```

My edit action

```php
public function editAction(Request $request, $id) {
    $em = $this->getDoctrine()->getManager();
    $entity = $em->getRepository('MyBundleItemBundle:Item')->find($id);
    $form = $this->createForm(new ItemType(), $entity);
    //$form->get('tags')->setValue('test text');
    // ^- this is what i would like to do -^
    // ...
}

```

While I am editing an item, How can I change form field value inside controller before rendering it?