useSignalEffect function

void useSignalEffect(dynamic cb(), { List<Object?> keys = const <Object>[], dynamic onDispose()?, String? debugLabel, })

Creates a new reactive effect and registers it with the widget's lifecycle.

The effect is automatically created on build and is disposed of when the widget is unmounted. Any reactive signal accessed inside the callback cb is tracked as a dependency, and the effect is executed automatically whenever those signals change.

Parameters

• cb: The effect callback to execute when tracked dependencies change.
• keys: A list of objects to watch. If any key changes, the effect is disposed and re-created.
• onDispose: An optional callback executed when the effect itself is disposed.
• debugLabel: An optional debug label to identify the effect in developer tools.

Example

import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:signals_hooks/signals_hooks.dart';

class LoggerWidget extends HookWidget {
  const LoggerWidget({super.key});

  @override
  Widget build(BuildContext context) {
    final count = useSignal(0);

    // Set up a side effect to log value changes
    useSignalEffect(
      () {
        debugPrint('The counter value is now: ${count.value}');
      },
      keys: [count],
      onDispose: () => debugPrint('Logger effect disposed'),
    );

    return TextButton(
      onPressed: () => count.value++,
      child: Text('Count: ${count.value}'),
    );
  }
}

Implementation

void useSignalEffect(
  dynamic Function() cb, {
  /// A list of objects to watch for changes.
  ///
  /// If any of the keys change, the effect will be re-created.
  List<Object?> keys = const <Object>[],

  /// A callback that is executed when the effect is disposed.
  dynamic Function()? onDispose,

  /// The debug label for the effect.
  String? debugLabel,
}) {
  useEffect(
    () => effect(cb, onDispose: onDispose, debugLabel: debugLabel),
    keys,
  );
  return;
}