? RealEventsBus

RealEventsBus is a small swift experiment package to implement a basic type-safe event bus mechanism.
Some other implementations in GitHub are the sources of inspiration for this package.

You can use it as replacement for standard NSNotification‘s one-to-many messaging.
It uses GCD for messagings, it’s thread-safe and, best of all, it’s type safe.

⭐️ Feature Highlights

  • It’s type safe
  • Implement custom messages; just set conformance to Event or BufferedEvent type
  • Messages/observers are posted and registered in thread safe
  • Easy to use; just one line to register and post events
  • Supports for buffered events (get the last value published by a bus)

?️ How It Works

This example uses enum as datatype for event.
Btw you can use any type you want as event, struct or class (see the other example below).
First of all we need to define a custom event; if your event is a group of different messages this is the best thing you can do:

public enum UserEvents: Event {
    case userDidLogged(username: String)
    case userLoggedOut
    case profileUpdated(fullName: String, age: Int)

Suppose you want to be notified about this kind of events in your UIViewController:

class ViewController: UIViewController {
    override func viewDidLoad() {

        Bus<UserEvents>.register(self) { event in
            switch event {
            case .profileUpdated(let fullName, let age):
                print("Profile updated with '\(fullName)', which is \(age) old")
            case .userDidLogged(let username):
                print("User '\(username)' logged in")
            case .userLoggedOut:
                print("User logged out")

    deinit {
        // While it's not required (it does not generate any leak) 
        // you may want to unregister an observer when it's not needed anymore.

When you need to post new events to any registered obserer like the one above just use post function:

Bus<UserEvents>.post(.userDidLogged(username: "danielemm"))


If your event is conform to BufferedEvent instead of Event you can use the lastValue() function to get the latest posted value into the bus. It’s like Rx.
Moreover: when a new observer is registered it will receive the last value posted into the bus, if any.

This is an example.

First of all we define the message:

public class CustomEvent: BufferedEvent {
    var messageValue: String
    var options: [String: Any?]?
    public init(value: String, options: [String: Any?]) {
        self.messageValue = value
        self.options = options


    // Post a new event
    Bus<CustomEvent>.post(.init(value: "Some message", options: ["a": 1, "b": "some"]))

    // At certain point in your code:
    let lastValue = Bus<CustomEvent>.lastValue() // print the type above!

Custom Dispatch Queue

You can also specify a queue where the message callback will be called.
By default the .main queue is used.

Bus<CustomEvent>.register(self, queue: .global()) { _ in // in background queue
   // do something


Swift Package Manager

To install it using the Swift Package Manager specify it as dependency in the Package.swift file:

dependencies: [
    .package(url: "https://github.com/malcommac/RealEventsBus.git", branch: "main"),


Not yet supported.


This little experiment was created by Daniele Margutti.
If you like it you can fork or open a PR or report an issue.
If you want to support my work just take a look at my Github Profile.


It’s the MIT license.


View Github