core_bus 1.0.1

A lightweight, type-safe Event Bus for Dart with optional event replaying. Decouples asynchronous code with minimal overhead.

core_bus

core_bus
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A small, tight, and type-safe Event Bus for Dart.

Unlike traditional event buses that use a single global stream of dynamic objects, core_bus gives each event its own typed stream. This eliminates manual casting and improves performance by only notifying relevant listeners.

Features

• Small & Tight: No external dependencies other than meta and test.
• Type-Safe: Leverage Dart's type system to ensure listeners receive the correct data types.
• Optional Replay: New listeners can automatically receive the last $N$ events emitted.
• Decoupled: Ideal for large applications or game engines (like Flame) where decoupling is critical.

Getting Started

Define your events as constants:

const userLogin = Event<String>.broadcast(name: 'userLogin');
const themeColor = Event<Color>.replay(name: 'themeColor', limit: 1);

Listen and post:

final bus = EventBus();

userLogin.on(bus).listen((name) => print('Hello, $name!'));

userLogin.post(bus, 'codefu');

Performance

This library is designed for high-performance and minimal object allocation.

• Direct Callbacks: For performance-critical code, use addListener / removeListener. This bypasses Dart's StreamController overhead and is significantly faster.
• Reactive Streams: Use .on(bus) for a convenient reactive API when convenience is more important than raw throughput.

Benchmarks

Running the included benchmark (dart run benchmark/speed_benchmark.dart) typically shows that the Callback API is ~2.5x - 3x faster than the Stream API for high-frequency event distribution.

API	Speed (Avg)
Callback API	~0.06μs per post
Stream API (Sync)	~0.17μs per post