ChangeNotifierProvider<NotifierT extends ChangeNotifier?> class final

Creates a ChangeNotifier and exposes its current state.

Combined with ChangeNotifier, ChangeNotifierProvider can be used to manipulate advanced states, that would otherwise be difficult to represent with simpler providers such as Provider or FutureProvider.

For example, you may have a todo-list, where you can add and remove and complete a todo. Using ChangeNotifier, you could represent such state as:

class TodosNotifier extends ChangeNotifier {
  List<Todo> todos = [];

  void add(Todo todo) {
    todos.add(todo);
    notifyListeners();
  }

  void remove(String todoId) {
    todos.removeWhere((todo) => todo.id == todoId);
    notifyListeners();
  }

  void toggle(String todoId) {
    final todo = todos.firstWhere((todo) => todo.id == todoId);
    todo.completed = !todo.completed;
    notifyListeners();
  }
}

Which you can then pass to a ChangeNotifierProvider like so:

final todosProvider = ChangeNotifierProvider<TodosNotifier, List<Todo>>((ref) => TodosNotifier());

And finally, you can interact with it inside your UI:

Widget build(BuildContext context, WidgetRef ref) {
  // rebuild the widget when the todo list changes
  List<Todo> todos = ref.watch(todosProvider).todos;

  return ListView(
    children: [
      for (final todo in todos)
        CheckboxListTile(
           value: todo.completed,
           // When tapping on the todo, change its completed status
           onChanged: (value) => ref.read(todosProvider.notifier).toggle(todo.id),
           title: Text(todo.description),
        ),
    ],
  );
}

Inheritance

Object
ProviderOrFamily
ProviderBase<NotifierT>
ChangeNotifierProvider

Annotations

@publicInLegacy

Constructors

ChangeNotifierProvider.new(NotifierT _createFn(Ref ref), {String? name, Iterable<ProviderOrFamily>? dependencies, bool isAutoDispose = false, Retry? retry}): Creates a ChangeNotifier and exposes its current state.

Properties

argument → Object?: If this provider was created with the .family modifier, argument is the variable that was used.
finalinherited
dependencies → Iterable<ProviderOrFamily>?: The list of providers that this provider potentially depends on.
finalinherited
from → Family?: If this provider was created with the .family modifier, from is the .family instance.
finalinherited
hashCode → int: The hash code for this object.
no setterinherited
isAutoDispose → bool: Whether the state associated to this provider should be disposed automatically when the provider stops being listened.
finalinherited
name → String?: A custom label for providers.
finalinherited
notifier → Refreshable<NotifierT>: Obtains the ChangeNotifier associated with this provider, without listening to state changes.
no setter
retry → Retry?: The default retry logic used by providers associated to this container.
finalinherited
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

create(Ref ref) → NotifierT: @nodoc
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
overrideWith(Create<NotifierT> create) → Override: Override the provider with a new initialization function.
inherited
toString() → String: A string representation of this object.
inherited

Operators

operator ==(Object other) → bool: The equality operator.
inherited

Constants

autoDispose → const AutoDisposeChangeNotifierProviderBuilder: Marks the provider as automatically disposed when no longer listened to.
family → const ChangeNotifierProviderFamilyBuilder: A group of providers that builds their value from an external parameter.