Event Emitter
An Event-based system, highly inspired by NodeJS's Event Emitter. 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:
dart 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: $data'));
events.emit('message', 'Hello World');
events.emit('message', 42);
// [Output]
// String: Hello World
// Integer: 42
To remove a specific listener, you can use the subscription to stop it.
final listener = events.on('message', ... ));
listener.cancel();
Remove listeners, by targeting a type, topic and callback.
// Remove all listeners
events.off();
// Remove listeners of type `String`
events.off<String>();
// Remove listeners on topic `message`
events.off(topic: 'message');
// Remove listeners of type `String` on topic `message`
events.off<String>(topic: 'message');
Why is this package different?
events_emitter implements the Event-based system using streams, then wraps it into a class that manages the callbacks, to make it more like what people are used to see in an EventEmitter. This allows you also to use the streams instead of callbacks if needed.
And something very important, events_emitter allows you to use type-safe events, so you can use the same topic for different data types. Not having to worry about the wrong type being passed in.
Example
The EventEmitter class can be used by itself or can be extended to create a custom event emitter.
import 'package:events_emitter/events_emitter.dart';
class Person extends EventEmitter {
String name;
Person(this.name);
void say(String message) => emit('say', message);
void eat(String food) => emit('eat', food);
void jump(double height) => emit('jump', height);
}
void main() {
final person = Person('John');
person.on('say', (String message) => print('${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:
307 Dec 24, 2022
89 Jan 5, 2023
5 Dec 15, 2022
2 Jul 8, 2022
21 Oct 18, 2022
5 Dec 25, 2022
22 Dec 29, 2022
132 Dec 14, 2022
477 Dec 31, 2022
98 Oct 31, 2022