swift-event-broadcasting

swift-event-broadcasting is a library for creating and observing events. It is similar in function to the events module in Node.js.

Here, an EventBroadcaster is the analogue of Node.js EventEmitter, and an event subscriber is the analogue of an event handler.

Features

"Set it and forget it" event subscription
Support for broadcasting multiple event types
Hassle-free unsubscribe mechanism for Hashable subscribers
Fully customizable event queueing and dispatching

Quick start

Create an event broadcaster

Extend EventBroadcaster or implement the EventBroadcasting protocol:

import Events

class GPSService: EventBroadcaster {
}

class GPSServiceAlternate: EventBroadcasting {
  private let broadcaster: EventBroadcaster = EventBroadcaster()

  func subscribe(...) { broadcaster.subscribe(...) }
  ...
  func broadcast(...) { broadcaster.broadcast(...) }
}

Subscribe to an event broadcaster

Subscribe with an event type, the event handler as a closure, and optionally an associated AnyHashable.

Without an AnyHashable, a SubscriberId will be returned. If you intend on unsubscribing (removing) the event handler, then you should store the subscriber id to call unsubscribe() later.

let gpsService = GPSService()

// Subscribe
let subscriberId = gpsService.subscribe(to: "locationUpdate") {
  print("location updated")
}

// Broadcast
gpsService.broadcast(Event(eventType: "locationUpdate"))
// prints "location updated"

// Unsubscribe
gpsService.unsubscribe(id: subscriberId, from: "locationUpdate")

With an AnyHashable, no subscriber id will be returned. To unsubscribe, pass the same AnyHashable.

let gpsService = GPSService()
let someHashable: AnyHashable = ...

// Subscribe
gpsService.subscribe(someHashable, to: "locationUpdate") {
  print("location updated")
}

// Broadcast
gpsService.broadcast(Event(eventType: "locationUpdate"))
// prints "location updated"

// Unsubscribe
gpsService.unsubscribe(subscriber: someHashable, from: "locationUpdate")