flutter mix optional and named arguments in a function

Question

I have a simple problem but I cannot find an answer to my question.

Is there a way to mix : optional arguments with default value and required named arguments in a flutter function ?

I need something like that but this exemple doesn't works in flutter.

 Future<void> getNationalRanking({required String connectedUserId}, [countryCode = "FR"]) async {
// blabla 
}

it might be a stupid syntax that I don't know.

Thanks for your help

Answer 1

Named parameters are already optional if you don't make them required and either make them nullable or provide a default value. For example:

Future<void> getNationalRanking({
  required String connectedUserId,
  String? countryCode,
}) async {
  countryCode ??= "FR";
  ...
}

or:

Future<void> getNationalRanking({
  required String connectedUserId,
  String countryCode = "FR",
}) async {
  ...
}

Your example attempts to mix named parameters with optional positional parameters, but using both is not allowed. From the Dart Language Tour:

A function can have any number of required positional parameters. These can be followed either by named parameters or by optional positional parameters (but not both).

Also see https://github.com/dart-lang/language/issues/1076.