events_emitter 0.2.0

An intuitive Event-based system, inspired by NodeJS's Event Emitter. Allows for multiple data types with type safety. Based on JavaScript and suitable for Dart and Flutter.

Event Emitter

A Event-based system, highly inspired by NodeJS's EventEmitter. This implementation uses generic types to allow for multiple data types, while still being intuitive.

Based on JavaScript and suitable for Dart and Flutter with type safety.

Features

• Attach multiple listeners to an event.
• Listen to a topic and data type.
• Emit a message on a specific topic to be broadcasted to all listeners.
• Type safety
• Use callbacks with EventEmitter.
• Use streams with EventStreamEmitter.
• Can be extended to create custom event emitter objects.

Getting started

Install it using pub:

flutter pub add events_emitter

And import the package:

import 'package:events_emitter/events_emitter.dart';

Usage

final events = EventEmitter();

events.on('message', (String data) => print('String: $data'));
events.on('message', (int data) => print('Integer: $data'));

events.emit('message', 'Hello World');
events.emit('message', 42);

// [Output]
// String: Hello World
// Integer: 42

To remove a specific listener, you can use the subscription to stop it.

final listener = events.on('message', ... ));
listener.cancel();

Remove listeners, by targeting a type, topic and callback.

// Remove all listeners
events.off();

// Remove listeners of type `String`
events.off<String>();

// Remove listeners on topic `message`
events.off(topic: 'message');

// Remove listeners of type `String` on topic `message`
events.off<String>(topic: 'message');

Why is this package different?

events_emitter implements the Event-based system using streams, then wraps it into a class that manages the callbacks, to make it more like what people are used to see in an EventEmitter. This allows you also to use the streams instead of callbacks if needed.

And something very important, events_emitter allows you to use type-safe events, so you can use the same topic for different data types. Not having to worry about the wrong thing being passed in.

GitHub

The package code is available on Github: Dart - EventEmitter

Example

The EventEmitter class can be used by itself or can be extended to create a custom event emitter.

import 'package:events_emitter/events_emitter.dart';

class Person extends EventEmitter {
    String name;

    Person(this.name);

    void say(String message) => emit('say', message);
    void eat(String food) => emit('eat', food);
    void jump(double height) => emit('jump', height);
}

void main() {
  final person = Person('John');

  person.on('say', (String message) => print('${person.name} said: $message'));
  person.on('eat', (String food) => print('${person.name} ate $food'));
  person.on('jump', (double height) => print('${person.name} jumped $height meters'));

  person.say('I\'m a human!');
  person.eat('apple');
  person.jump(0.5);

  // [Output]
  // John said: I'm a human!
  // John ate apple
  // John jumped 0.5 meters
}

More examples:

• EventEmitter
• EventStreamEmitter
• Sync
• Extendable