notifier_plus

notifier_plus is a high-performance Flutter state management library designed to optimize Listenable updates. Created by tachibana-shin, this library eliminates unnecessary UI rebuilds caused by ValueNotifier and Listenable.merge.

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📖 Table of Contents

• Why notifier_plus?
• Installation
• Core Classes
  • Notifier<T> - Optimized ValueNotifier
  • ComputedNotifier<T> - Derived State Management
  • ComputedAsyncNotifier<T> - Async Computed State
• Watch Widgets
• Utilities
• Comparison Table
• Contributing
• License

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📌 Why notifier_plus?

🚀 The Problem with ValueNotifier and Listenable.merge

• ValueNotifier causes redundant UI rebuilds when updated consecutively:

  a.value++;
  a.value++;  // Causes two rebuilds, but only one is needed

• Listenable.merge invokes multiple rebuilds when multiple dependencies update:

  a.value++;
  b.value++;  // Triggers two rebuilds instead of one

✅ Solution: notifier_plus

• Batches multiple updates within the same frame to trigger only one rebuild.
• Efficient state management that reduces unnecessary UI updates.
• Easy to use with ValueNotifier-like API but optimized for performance.

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📦 Installation

Add to pubspec.yaml:

dependencies:
  notifier_plus:
    git:
      url: https://github.com/tachibana-shin/notifier_plus.git

Import it:

import 'package:notifier_plus/notifier_plus.dart';

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🟢 Core Classes

Notifier<T> - Optimized ValueNotifier

A ChangeNotifier implementation that ensures updates are only triggered once per frame.

final counter = Notifier<int>(0);
counter.addListener(() {
  print("Counter updated: ${counter.value}");
});
counter.value++;  // Only one listener call per frame

✅ Features:

• Prevents redundant updates.
• Implements ValueListenable<T> for seamless integration.

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ComputedNotifier<T> - Derived State Management

Computes a value based on other Notifier dependencies.

final a = Notifier<int>(1);
final b = Notifier<int>(2);
final sum = ComputedNotifier(() => a.value + b.value, depends: [a, b]);

sum.addListener(() {
  print("Sum updated: ${sum.value}");
});

✅ Features:

• Automatically tracks dependencies.
• Only updates when dependent values change.

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ComputedAsyncNotifier<T> - Async Computed State

Handles derived state that depends on asynchronous computations.

final asyncSum = ComputedAsyncNotifier<int>(
  () async => await fetchData(),
  depends: [a, b]
);

✅ Features:

• Supports async state calculations.
• Notifies listeners only when computation completes.

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🏗 Watch Widgets

Efficient UI rebuilding for state changes.

WatchComputed<T> - Watches a Single ComputedNotifier

WatchComputed<int>(
  computed: sum,
  builder: (context, value) {
    return Text("Sum: $value");
  },
);

WatchAsyncComputed<T> - Watches an Async Computed Value

WatchAsyncComputed<int>(
  computed: asyncSum,
  builder: (context, value) {
    return value == null ? CircularProgressIndicator() : Text("Sum: $value");
  },
);

WatchComputes<T> - Watches Multiple ComputedNotifiers

WatchComputes<int>(
  computes: [a, b],
  builder: (context) {
    return Text("A: ${a.value}, B: ${b.value}");
  },
);

WatchNotifier<T> - Watches Multiple ChangeNotifiers

WatchNotifier(
  depends: [a, b],
  builder: (context) {
    return Text("State changed: A=${a.value}, B=${b.value}");
  },
);

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⚡ Utilities

oneCallTask(VoidCallback callback)

A helper function to debounce state updates within the same frame.

final debouncedUpdate = oneCallTask(() {
  print("Updated!");
});
debouncedUpdate(); // Calls once per frame

watch(List<Listenable> depends, VoidCallback callback, {bool immediate})

Registers a callback that listens to multiple Listenables efficiently.

watch([a, b], () {
  print("A or B changed");
});

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📌 Comparison Table

Feature	notifier_plus
Prevents redundant UI rebuilds	✅
Optimized ValueNotifier replacement	✅
Efficient dependency tracking	✅
Supports async computed values	✅
Lightweight & easy to use	✅

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🛠 Contributing

Pull requests are welcome! Feel free to submit issues or feature requests.

📜 License

MIT License. See LICENSE for details.