event_kit

This is a simple library for implementing event subscription APIs. This project is inspired by event-kit.

Implementing Event Subscription APIs

import 'package:event_kit/event_kit.dart';

class User {
  final Emitter<String> _emitter = new Emitter<String>();

  String _name = '';

  Disposable onDidChangeName(void handler(String name)) =>
      _emitter.on('did-change-name', handler);

  void set name(String name) {
    if (_name != name) {
      _name = name;
      _emitter.emit('did-change-name', [name]);
    }
  }
}

In the example above, we implement onDidChangeName on the user object, which will register callbacks to be invoked whenever the user's name changes. To do so, we make use of an internal Emitter instance. We use on to subscribe the given callback in onDidChangeName, and emit in setName to notify subscribers. Finally, when the User instance is destroyed we call dispose on the emitter to unsubscribe all subscribers.

Consuming Event Subscription APIs

Emitter.on returns a Disposable instance, which has a dispose method. To unsubscribe, simply call dispose on the returned object.

import 'package:event_kit/event_kit.dart';

var subscription = user.onDidChangeName((name) => print('My name is ${name}'));
// Later, to unsubscribe...
subscription.dispose();

You can also use CompositeDisposable to combine disposable instances together.

import 'package:event_kit/event_kit.dart';

var subscriptions = new CompositeDisposable();
subscriptions.add(user1.onDidChangeName((name) => print('User 1: ${name}')));
subscriptions.add(user2.onDidChangeName((name) => print('User 2: ${name}')));

// Later, to unsubscribe from *both*...
subscriptions.dispose();

Features and bugs

Please file feature requests and bugs at the issue tracker.

Libraries

event_kit

A simple library for implementing event subscription APIs.