How to change Request before submitting data to a Form?

Question

I'm building an API with Symfony 3 following the JSON API specification (Documentation).

When submitting new data, the request has this format :

{
  "type": "entity",
  "id"  : null,
  "attributes" : {
    "name" : "Test name"
  }
}

But the problem is the request does not fit the format expected by symfony's Forms because of the extra object attributes.

So I want to be able to transform the request before the form submit in order to make the form able to populate the underlying Entity.

I have tried to register an FormEvents:PRE_SUBMIT and do the logic in it but it seems I have no access to the Request content.

$builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) {
            $data = $event->getData();

            var_dump($data);
            die();
        });

The $event->getData() is null.

I have also see there is possibility to register DataTransformer but it is registered per field, and has no access to the Request too.

I don't want to do it manually in the Controller as this will occur on all my forms (or at least the majority), so I search for a more generic way to transform the request, but at this point I can't figure out how to do this.

Thanks for help.

Answer 1

Your EventListener does not have access to your Request, nor does your Form itself.

The best and cleanest way to do this in my opinion would be to define a custom RequestHandler for your Forms, extending the NativeRequestHandler that parses your Request by default.

Then you only need to execute $builder->setRequestHandler() to apply this to your Forms.