Signal<T> class

A Signal holds a single reactive value of type T.

When its value is read, it automatically registers the currently active consumer as an observer. When its value changes, it notifies all observers.

Supports automatic lifecycle management via autoDispose and lifecycle callbacks onListen and onDispose.

Implementers

• AsyncSignal

Available extensions

• HydratedSignalExtension
• SignalFlutterExtension

Constructors

Signal(T _value, {String? name, bool autoDispose = false, void onDispose()?, void onListen()?})

Creates a new Signal with the given initial value and optional lifecycle callbacks.

Properties

autoDisposeEnabled ↔ bool

Whether this signal should automatically dispose of its resources when it has no observers.

getter/setter pair

hashCode → int

The hash code for this object.

no setter, inherited

isDisposed ↔ bool

Tracks whether the signal is currently in a disposed state.

getter/setter pair

name → String?

Optional name for debugging and observation.

final

observers → Set<Consumer>

The set of active consumers currently observing this node.

final, inherited

onDisposeCallback ↔ void Function()?

Callback executed when this signal is disposed (e.g. observers drop to 0 under autoDispose).

getter/setter pair

onListenCallback ↔ void Function()?

Callback executed when this signal is first observed or revived after auto-disposal.

getter/setter pair

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

value ↔ T

Gets the current value of the signal.

getter/setter pair

Methods

addChangeListener(void listener(T previous, T current)) → void

Registers a lightweight value-change callback that does not count as a reactive observer for auto-disposal.

addObserver(Consumer consumer) → void

Registers a consumer to observe changes on this node.

autoDispose({void onDispose()?}) → Signal<T>

Configures this signal to automatically dispose when all observers are removed, returning the signal itself to allow fluent builder chaining.

dispose() → void

Disposes of the resources associated with this signal, executing the onDisposeCallback.

hydrate({required String key, required T fromJson(String value), required String toJson(T value), SignalStorage? storage}) → Signal<T>

Available on Signal<T>, provided by the HydratedSignalExtension extension

Hydrates (persists) the current signal using the provided storage or globalSignalStorage.

listen(void listener(T previous, T current), {bool fireImmediately = false}) → SignalSubscription<T>

Listens to value changes without creating an Effect manually.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

notifyObservers() → void

Notifies all registered observers that the value of this node has changed.

inherited

peek() → T

Returns the current value without registering a reactive dependency.

removeChangeListener(void listener(T previous, T current)) → void

Removes a callback previously registered with addChangeListener.

removeObserver(Consumer consumer) → void

Unregisters a consumer from observing this node.

setValueSilently(T newValue) → void

Sets the value of this signal without notifying its observers.

toString() → String

A string representation of this object.

override

watch(BuildContext context) → T

Available on Signal<T>, provided by the SignalFlutterExtension extension

Subscribes the current BuildContext (widget) to this signal.

Operators

operator ==(Object other) → bool

The equality operator.

inherited