statusline.dart

class StatusLine extends StatelessWidget {
  final Status status;
  StatusLine({this.status: Status.failed});
  @override
  Widget build(BuildContext context) {
    // This local variable is non-nullable, but not initialized.
    String statusText;
    if (status == Status.ok) {
      statusText = 'Update succeeded';
    } else {
      statusText = 'Update failed';
    }
    // By this point, Dart knows statusText isn't null, as we've
    // assigned a value in both the if- and else-statements. Thus
    // we can pass it to the Text widget -- which doesn't accept
    // nullable Strings -- without getting an error.
    return Text(statusText);
  }