Symfony 3.4 Ajax in Form event

Question

In my project, the form allow user select a Map in a SelectBox. When Map Selectbox change, the options in GroupLayer Selectbox also change depend on which Map is selected. I see exactly Symfony document for my case in: How to Dynamically Modify Forms Using Form Events Howerver, in example code:

$formModifier = function (FormInterface $form, Sport $sport = null) {
        $positions = null === $sport ? array() : $sport->getAvailablePositions();

        $form->add('position', EntityType::class, array(
            'class' => 'App\Entity\Position',
            'placeholder' => '',
            'choices' => $positions,
        ));
    };

I don't know where the getAvailablePositions() function should be and what is the returning of this function?. I think this function will be placed in Sport Entity. Is that right, in Sport Entity, could I query the Position Entity with Doctrine ORM queryBuilder?

Answer 1

with this formModifier you only change the fields that your form have. I don't know where you have the relation between Map and GroupLayer, but this relation is what you need to search. For example, if you have a OneToMany relation beetween the entities you can do:

$map->getGroupLayers();

this was the choices for the selector.

In the other hand you can use a custom method from the GroupLayer repository with the map as parameter or a service that search for the related GroupLayers from a map, it's up to you and your architecture.

Edit #1

With your new info i guess that your code seem near like this:

$formModifier = function (FormInterface $form, Map $map = null) {
    $groupLayers = null === $map ? array() : $map->getGroupLayers();

    $form->add('position', EntityType::class, array(
        'class' => 'App\Entity\GroupLayer',
        'placeholder' => '',
        'choices' => $groupLayers,
    ));
};

$builder->addEventListener(
    FormEvents::PRE_SET_DATA,
    function (FormEvent $event) use ($formModifier) {
        // this would be your entity, i.e. SportMeetup
        $data = $event->getData();

        $formModifier($event->getForm(), $data->getMap());
    }
);

$builder->get('sport')->addEventListener(
    FormEvents::POST_SUBMIT,
    function (FormEvent $event) use ($formModifier) {
        // It's important here to fetch $event->getForm()->getData(), as
        // $event->getData() will get you the client data (that is, the ID)
        $map = $event->getForm()->getData();

        // since we've added the listener to the child, we'll have to pass on
        // the parent to the callback functions!
        $formModifier($event->getForm()->getParent(), $map);
    }
);

I hope this can help you