EventTruck

A Lightweight Event Bus for Efficient Event Communication

EventTruck is a lightweight, extensible, and type-safe event bus system for managing event-driven architecture in Dart/Flutter applications. It provides a streamlined API for broadcasting and listening to events, with optional support for event observation, debugging, and logging.

---

Features

• 📢 Broadcast Events: Send events to multiple listeners efficiently.
• 🔍 Optional Event Observation: Track and debug emitted events using a customizable observer.
• 🔄 Type-Safe Event Handling: Filter events by type and ensure safety in event handling.
• 🚦 Scoped Lifecycle Management: Clean up resources by properly disposing of the event bus.

---

Getting Started

Installation

Add EventTruck to your Dart or Flutter project by including the following in your pubspec.yaml file:

dependencies:
  event_truck: <latest_version>

Then, run:

flutter pub get

---

Usage

Setting Up an EventTruck

Create an instance of the EventTruck to handle events:

final eventTruck = EventTruck();

Listening for Events

Use the on<T>() method to subscribe to specific event types:

// Sealed class
sealed class Event {}

class ClickEvent extends Event {
  final String buttonId;
  ClickEvent(this.buttonId);
}

class TextEvent extends Event {
  final String text;
  TextEvent(this.text);
}


// Listen to all events of type `Event` (base class or subclasses)
eventTruck.on<Event>((event) => switch(event) {
    ClickEvent() => print(event.buttonId),
    TextEvent() => print(event.text),
});

// or

eventTruck.on<ClickEvent>((event) => print(event.buttonId));
eventTruck.on<TextEvent>((event) => print(event.text));

Emitting Events

Use the add() method to emit events:

eventTruck.add(ClickEvent('submit_button'));
eventTruck.add(TextEvent('Hello World!'));

Using an Observer

To monitor all events for logging or debugging purposes, implement the EventTrackObserver interface:

class DebugObserver implements EventTrackObserver {
  @override
  void onEvent<T>(T event) {
    print('Observed event: $event');
  }
}

void main() {
  EventTruck.observer = DebugObserver();
  final eventTruck = EventTruck();
  eventTruck.add('Tracking this event');
}

Cleaning Up

Dispose of the EventTruck instance when it's no longer needed:

eventTruck.dispose();

---

API Reference

EventTruck

on

Subscribe to events of a specific type.

Parameters: callback: A function that handles the specific event type T.

Returns: A stream controller of events filtered by type T.

Example:

StreamController<ClickEvent> _streamController = eventTruck.on<ClickEvent>((event) {
  print('Received click event: $event');
});

_streamController.close();

---

add(Event event)

Emit a new event to all listeners. Parameters:

event: The event to be added to the event stream.

Example:

eventTruck.add('New message event');

---

dispose()

Clean up resources by closing the underlying StreamController. Example:

eventTruck.dispose();

---

EventTrackObserver

An interface to track emitted events.

onEvent

Handle and log emitted events.

Parameters: event: The event emitted through the EventTruck.

Example:

class MyObserver implements EventTrackObserver {
  @override
  void onEvent<E, T>(EventTruck<E> truck, T event) {
    print('Logged event: $event');
  }
}

---

Best Practices

1. Disposal: Always call dispose() to avoid memory leaks in long-running applications.
2. Observer Usage: Use the observer for debugging in development but avoid excessive logging in production.
3. Type-Safe Events: Leverage the generic API to maintain type safety when working with events.
4. Minimized Scope: Use separate instances of EventTruck for different parts of your app to reduce unnecessary event propagation.

---

Example Project

Here’s a simple example demonstrating the usage of EventTruck:

void main() {
  final eventTruck = EventTruck();

  // Listening for string events
  eventTruck.on<String>((event) {
    print('String Event: $event');
  });

  // Emitting different events
  eventTruck.add('Hello, EventTruck!');
  eventTruck.add(123);

  // Using an observer
  EventTruck.observer = DebugObserver();

  // Clean up resources
  eventTruck.dispose();
}

class DebugObserver implements EventTrackObserver {
  @override
  void onEvent<T>(T event) {
    print('Debug Observer: $event');
  }
}

Codecov