class final

Creates a StateNotifier and exposes its current state.

This provider is used in combination with package:state_notifier.

Combined with StateNotifier, StateNotifierProvider 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 StateNotifier, you could represent such state as:

class TodosNotifier extends StateNotifier<List<Todo>> {
  TodosNotifier(): super([]);

  void add(Todo todo) {
    state = [...state, todo];
  }

  void remove(String todoId) {
    state = [
      for (final todo in state)
        if (todo.id != todoId) todo,
    ];
  }

  void toggle(String todoId) {
    state = [
      for (final todo in state)
        if (todo.id == todoId) todo.copyWith(completed: !todo.completed),
    ];
  }
}

Which you can then pass to a StateNotifierProvider like so:

final todosProvider = StateNotifierProvider<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);

  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<ValueT>
StateNotifierProvider

Available extensions

ProviderListenableSelect

Annotations

@publicInLegacy

Constructors

StateNotifierProvider.new(NotifierT _create(Ref ref), {String? name, Iterable<ProviderOrFamily>? dependencies, bool isAutoDispose = false, Retry? retry}): Creates a StateNotifier 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 StateNotifier associated with this provider, without listening to state changes.
no setter
retry → Retry?: The retry strategy to use when a provider fails.
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
select<OutT>(OutT selector(InT value)) → ProviderListenable<OutT>: Available on ProviderListenable<InT>, provided by the ProviderListenableSelect extension
Partially listen to a provider.
toString() → String: A string representation of this object.
inherited

Operators

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

Constants

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