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Solution: State Management

Solution: State Management

Explore solutions to the Riverpod challenges.

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Solutions

Follow the steps below and compare your answers to each challenge you attempted in the previous lesson.

Challenge 1: Add Packages

We go to line 16 of the pubspec.yaml file and replace # TODO-1: Add flutter_riverpod package with the line below:

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  flutter_riverpod: ^1.0.0

Challenge 2: Complete the TasksChangeNotifier class

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import 'dart:collection';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../models/task.dart';
final tasksProvider = ChangeNotifierProvider<TasksChangeNotifier>((ref) => TasksChangeNotifier());
class TasksChangeNotifier extends ChangeNotifier {
  final List<Task> _tasks = [];
  UnmodifiableListView<Task> get tasks {
    return UnmodifiableListView(_tasks);
  }
  int get tasksLength => _tasks.length;
  void addTask(String task) {
    _tasks.add(Task(name: task));
    notifyListeners();
  }
  void deleteTask(index) {
    _tasks.removeAt(index);
    notifyListeners();
  }
  void toggleDone(index) {
    _tasks[index].isDone = !_tasks[index].isDone;
    notifyListeners();
  }
}

  1. We first import the flutter_riverpod package (line 4).

  2. On line 7, we declare a tasksProvider object, which creates and exposes an instance of TasksChangeNotifier to be accessed elsewhere within the application.

  3. Line 19 allows us to add a single task to the list of tasks given its string name. Note that after adding a new task to the list, we call the notifyListeners() method (line 20), which notifies the users of the TasksChangeNotifier object that the object changes. ...