enhanced_change_notifier

Support for targeted notifications on object property changes.

Enhanced ChangeNotifiers introduce three new features in addition to all existing ChangeNotifier capabilities in Flutter Core:

• target: notifies listeners at the moment a specified property changes.
• once: notifies listeners only once at the moment of a change.
• immediate: allows notifications to be sent immediately after a listener is registered and upon subsequent changes.

Platform Support

Requirements

• Flutter >=3.0.0 <4.0.0
• Dart >=2.17.0

Getting started

published on pub.dev, run this Flutter command

flutter pub add enhanced_change_notifier

Usage in Dart

Multiple properties or Mutable data types, extending EnhancedChangeNotifier directly to meet flexible requirements like cache or targeted listener.

import 'package:enhanced_change_notifier/enhanced_change_notifier.dart';

class AppModel extends EnhancedChangeNotifier {

  String? get token => super.properties["token"];
  set token(String? token) {
    super.properties["token"] = token;
  }
}

// GlobalFactory helps create a global singleton instance.
final GlobalFactory<AppModel> appStateModel = GlobalFactory(() => AppModel());

function _e_anyChangedListener() {
  print("any property is changed");
}

// Register all types of listeners
appStateModel.getInstance().addListener(() => print("any property is changed"));
appStateModel.getInstance().addListener((String property) => print("$property is changed"), target: 'token');
appStateModel.getInstance().addListener((String property) => print("$property is changed, will notify only once."), target: 'token', once: true);
appStateModel.getInstance().addListener((String property) => print("$property is changed, will send immediately after listener is registered."), target: 'token', immediate: true);

// Remove a specific listener
appStateModel.getInstance().removeListener(_e_anyChangedListener);

Signal A single implementation buffers pipelined listener pending a release signal.

import 'package:enhanced_change_notifier/signal.dart';

Signal isConsumerReady = Signal();
isConsumerReady.value = false;

// Register listener consumed immediately or awaited once via Signal(True).
isConsumerReady.promise(() => print("Task 1 executed"));
isConsumerReady.promise(() => print("Task 2 executed"));

// Release delayed signal
Future.delayed(Duration(milliseconds: 300), () => isConsumerReady.value = true);

EnhancedLatchNotifier supports complex data types for delayed notifications, unlike Signal which is limited to boolean values

final GlobalFactory<DelayedLatch> latchDemo = GlobalFactory(() => DelayedLatch());
latchDemo.getInstance().addListener((event) {
  if (event.actionId == "test") {
    print("triggered ==> ${event.actionId}, ${event.value}");
  }
});
// Fire latch and cache state event
latchDemo.getInstance().fire(LatchStateEvent("test", 99));
// Listener triggered when unlatch called
Future.delayed(const Duration(seconds: 3), () => latchDemo.getInstance().unlatch());

Additional information

Feel free to file an issue if you have any problem.