state_examples: common classes

list.extension.dart

// A simple helper function to allow us to immutably add to lists.
extension ImmutableList<T> on List<T> {
  List<T> concat(T item) => List<T>.from(<T>[...this, item]);
}

note.dart

// A simple widget for displaying individual notes.
class Note extends StatelessWidget {
  final String text;

  const Note({Key key, this.text}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 8.0),
      child: Text('Note: $text'),
    );
  }
}

notes.state.dart

// You can add equatable as a dependency to your pubspec.yaml
// https://pub.dev/packages/equatable/install
class NotesState extends Equatable {
  final List<String> notes;
  final String input;

  NotesState(
    this.notes,
    this.input,
  );

  @override
  List<Object> get props => [notes, input];

  @override
  bool get stringify => true;

  NotesState copyWith({
    List<String> notes,
    String input,
  }) {
    return NotesState(
      notes ?? this.notes,
      input ?? this.input,
    );
  }

  NotesState.initial()
      : notes = [],
        input = '';
}