class Null safety

Creates a StateNotifier and expose 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
ProviderBase<State>
AlwaysAliveProviderBase<State>
StateNotifierProvider

Mixed in types

StateNotifierProviderOverrideMixin<Notifier, State>

Annotations

@sealed

Constructors

StateNotifierProvider(Create<Notifier, StateNotifierProviderRef<Notifier, State>> create, {String? name, List<ProviderOrFamily>? dependencies, Family<dynamic, dynamic, ProviderBase>? from, Object? argument}): Creates a StateNotifier and expose its current state.

Properties

allTransitiveDependencies → List<ProviderOrFamily>?: All the dependencies of a provider and their dependencies too.
latefinalinherited
argument → Object?: If this provider was created with the .family modifier, argument is variable used.
finalinherited
dependencies → List<ProviderOrFamily>?: The list of providers that this provider potentially depends on.
latefinalinherited
from → Family<dynamic, dynamic, ProviderBase>?: If this provider was created with the .family modifier, from is the .family instance.
finalinherited
hashCode → int: The hash code for this object.
read-onlyinherited
name → String?: A custom label for providers.
finalinherited
notifier → AlwaysAliveProviderBase<Notifier>: Obtains the StateNotifier associated with this StateNotifierProvider, without listening to it.
final
originProvider → ProviderBase<Notifier>: The provider that will be refreshed when calling ProviderContainer.refresh and that will be overridden when passed to ProviderScope.
read-onlyinherited
runtimeType → Type: A representation of the runtime type of the object.
read-onlyinherited

Methods

create(covariant ProviderElementBase<State> ref) → State: Initializes the state of a provider
override
createElement() → ProviderElementBase<State>: An internal method that defines how a provider behaves.
override
noSuchMethod(Invocation invocation) → dynamic: Invoked when a non-existent method or property is accessed.
inherited
overrideWithProvider(StateNotifierProvider<Notifier, State> value) → Override: Overrides a provider with a value, ejecting the default behaviour.
inherited
overrideWithValue(Notifier value) → Override: Overrides a provider with a value, ejecting the default behaviour.
inherited
select<Selected>(Selected selector(State value)) → AlwaysAliveProviderListenable<Selected>: Partially listen to a provider.
inherited
toString() → String: A string representation of this object.
inherited
updateShouldNotify(State previousState, State newState) → bool: Called when a provider is rebuilt. Used for providers to not notify their listeners if the exposed value did not change.
override

Operators

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

Constants

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