ValueNotifierSignalMixin

ValueNotifierSignalMixin is a mixin for a Readonly Signal that implements ValueNotifier.

This allows you to use the signal as a ValueNotifier in Flutter widgets.

class MySignal extends Signal<int> with ValueNotifierSignalMixin<int> {
  MySignal(int value) : super(value);
}

void main() {
  final signal = MySignal(0);
  assert(signal is ReadonlySignal<int>);
  assert(signal is ValueNotifier<int>);
  final listener = () => print(signal.value);
  signal.addListener(listener);
  signal.value = 1;
  signal.removeListener(listener);
  signal.value = 2;
}

When addListener is called it will subscribe to the signal and call the listener when the signal changes.

Caution

By default the listener callback will subscribe to dependencies called inside the listener because it is an effect.

To prevent this you can use untracked to read the signal without subscribing to it.

final signal = MySignal(0);
final dep = signal(0);
final listener = () {
    untracked(() {
        print(signal.value);
        print(dep.value);
    });
};
signal.addListener(listener);

When removeListener is called with the same method it will unsubscribe from the signal.

When the signal is disposed it will remove all listeners.

ValueListenableBuilder

In Flutter you can use the ValueListenableBuilder widget to listen to a ValueNotifier.

import 'package:flutter/material.dart';
import 'package:signals/signals_flutter.dart';

final counter = signal(0);

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<int>(
      valueListenable: counter,
      builder: (context, value, child) {
        return Text('Count: $value');
      },
    );
  }
}