Symfony subfom can't acces unmapped data

Question

I'm trying to make a form with possible subforms ( which can be added/removed on click of add/remove ), it works, but I can't get the unmapped variable from the form

MainForm

    $builder
    ...
        ->add('courses', 'collection', array(
            'type' => new CoursesType(),
            'allow_add'    => true,
            'allow_delete'    => true,
            'prototype' => true,
        ))
    ...   

CoursesType form

    $builder
    ...
        ->add('map', 'file', array(
            'attr' => array(
                'maxsize'     =>'4M',
                'accept'      =>'image/*'
            ),
            'required' => false,
            'data_class' => null,
            'mapped' => false,
        ));
    ...    

The CoursesType form is mapped to an entity so I get the other form data, while I can't access the "map" field

Tried to dump the form, the data I get from "courses" , can't find "map" anywhere

EDIT 1: if I get rid of the mapping of courses to the entity "new CoursesType()" and add a mapping false, I get the data as I want(but in array), but this way I have to manually check all the data and add to a entity, can this be avoided ?

Answer 1

It is possible to string together $form->get() statements before the ->getData()

$courses = $form->get('courses')
foreach ($courses as $course) {
    $map = $course->get('map')->getData();
}

I don't know how this will work with adding and removing items from the collection but works ok for fixed collections