The argument type 'Function' can't be assigned to the parameter type 'void Function()?' Dart

Question

import 'package:flutter/material.dart';

class Answer extends StatelessWidget {
  final Function selectHandler;

  Answer(this.selectHandler);

  @override
  Widget build(BuildContext context) {
    return Container(
      width: double.infinity,
      color: Colors.pink,
      child: ElevatedButton(
        child: Text('Answer 1'),
        onPressed: selectHandler,
      ),
    );
  }
}

[screenshot of vscode][1]

I got this code that I use from a Dart (flutter) YouTube course (that is from 2019) and i get an error on the last "selectHandler" (after onPressed) -> "The argument type 'Function' can't be assigned to the parameter type 'void Function()?'" I don't really understand because it is working well in the video. I am pretty sure that the course is too old but if you can help me that could be cool. Thanks ! (PS: my flutter doctor is good)

Answer 1

Replace

final Function selectHandler;

with

final void Function() selectHandler;

see this ref doc