A mixin that adds tracking for the initial and previous values to a Signal.
TrackedSignalMixin stores the initialValue (the value the signal had when it was
created or initialized) and the previousValue (the value of the signal right before
the most recent update).
If you are looking for full undo/redo capabilities, use ChangeStackSignalMixin instead.
Example Usage#
import 'package:signals/signals.dart';
class MyTrackedSignal extends Signal<int> with TrackedSignalMixin<int> {
MyTrackedSignal(super.internalValue);
}
void main() {
final signal = MyTrackedSignal(0);
print('Initial: ${signal.initialValue}'); // Prints: "Initial: 0"
print('Previous: ${signal.previousValue}'); // Prints: "Previous: null"
signal.value = 1;
print('Initial: ${signal.initialValue}'); // Prints: "Initial: 0"
print('Previous: ${signal.previousValue}'); // Prints: "Previous: 0"
signal.value = 2;
print('Initial: ${signal.initialValue}'); // Prints: "Initial: 0"
print('Previous: ${signal.previousValue}'); // Prints: "Previous: 1"
}
This mixin only works with values that are immutable or are copied/cloned on mutation.
If the value is mutated directly in-place without re-assigning,
initialValue and
previousValue will end up pointing to the same modified instance as the current value.
Methods#
View Methods
T initialValue
The initial value the signal was created with
T? previousValue
Get the previous value (if exists)
trackedSignal#
Create a signal that stores the initial and previous value
TrackedSignal#
A signal that stores the initial and previous value
Constructors#
View Constructors
TrackedSignal(super.value, {TrackedSignalOptions? options, @Deprecated('Use options: TrackedSignalOptions(autoDispose: ...) instead') bool? autoDispose, @Deprecated('Use options: TrackedSignalOptions(name: ...) instead') String? debugLabel})
A signal that stores the initial and previous value
TrackedSignalOptions#
Configuration options for a TrackedSignal.
Constructors#
View Constructors
TrackedSignalOptions({super.name, super.autoDispose, super.watched, super.unwatched})
Creates a new TrackedSignalOptions instance.