flutter-examples/todo_list_using_provider/lib/models/todo.dart

import 'package:flutter/material.dart';

class Todo extends ChangeNotifier {
  final String id;
  String title;
  bool done;

  Todo({@required this.id, this.title, this.done = false});


  /// Toggles the value of the item and notify to listeners
  void toggle() {
    this.done = !this.done;
    notifyListeners();
  }
}