Navigator pass arguments with pushNamed

No need for onGenerateRoute. Simply use

var exampleArgument="example string";

Navigator.pushNamed(
    context,
    '/otherscreen',
    arguments: {'exampleArgument': exampleArgument},
);

and extract the arguments as follows:

@override
Widget build(BuildContext context) {
    final arguments = (ModalRoute.of(context)?.settings.arguments ?? <String, dynamic>{}) as Map;

    print(arguments['exampleArgument']);

    return Scaffold(...);
}