update symfony field on form submit

Question

lets say that i have a simple form like this:

class MyType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('field', 'text');

        // this is select
        $builder->add('field2', 'choice', array(
            'choices' => array(),
            'expanded' => false,
            'multiple' => false,
        ));
    }
}

now i want to update field2 options on form submit. so the flow is:

1. visit the page with empty form
2. fill field1 and submit the form
3. form will 'fail validation' as it is missing value for field2, but this time it ll render the form with options for field2 based on submitted value from field1
4. value for field2 is selected and together with field1 (filled in step 2) submitted
5. form validation pass

What i've tried

1.

How to Dynamically Modify Forms Using Form Events

here they discuss how to add new field based on submitted form, but i need to update already existing field. so in event function something like:

$form->get('field2')->**update**('choices', array(1=>'test'));

however i could not figure out how to do this as there is no function **update**

i can re-create field2 in form event like this:

$builder->get('field2')->remove();
$builder->add('field2', 'choice', array(...));

but this doesn't seems right.

2.

getting value of field1 in controller and pass it to my MyType as custom option and based on that either set or not choices on field2 during form creation.

my problem here is, that if i do this, i have to get the value directly from $request->query->get('field1'); and this is wrong. i need to let the form to process request and than get the value via $form->getData()->getField1() so the form has a chance to process my DataTransformer attached to field1

my code in controller is standard code generated by symfony2:

$entity = new Entity();
$form = $this->createCreateForm($entity);
$form->handleRequest($request);
$value = $form->getData()->getField1();

and now its too late to pass $value to form builder as the form is already created in createCreateForm()

any idea?

Answer 1

Can you try to replace, in your first tried solution, this block :

$builder->get('field2')->remove();
$builder->add('field2', 'choice', array(...));

By this one :

$builder->remove('field2');
$builder->add('field2', 'choice', array(...));