Causality

A very simple event bus for Swift. Events may have associated data and are fully typed. All publish/subscribe methods are thread-safe.

Installation

Swift Package Manager

Add the Causality package to the dependencies within your application’s Package.swift file. Substitute “x.y.z” with the latest Causality release.

.package(url: "https://github.com/dannys42/Causality.git", from: "x.y.z")

Add Causality to your target’s dependencies:

.target(name: "example", dependencies: ["Causality"]),

Usage

Just an event (no data)

The simplest event to manage has no associated data.

Declare Events

This declares an event called aTriggerEvent that has no associated data.

struct MyEvents {
    static let aTriggerEvent = Causality.Event<NoSimpleEventMessage>(name: "A Trigger")
}

Subscribe to events

To subscribe to this event:

let subscription = Causality.bus.subscribe(MyEvents.aTriggerEvent) { _ in
    print("Event happened")
}

Publish events

To publish/post an event of this type:

Causality.bus.publish(MyEvents.aTriggerEvent)

An event with associated data

Events can include data of any type (referred to as a “message”). The event label is fully type specified with the message. So a subscriber will have a fully typed message available to its handler.

Define the Message

A message can be a standard Swift type like Int, String, etc. Or it can be a struct or class. In this example, we’ll declare a struct:

struct InterestingMessage: Causality.Message {
    let string: String
    let number: Int
}

Declare the event

struct MyEvents {
    static let interestingEvent = Causality.Event<InterestingMessage>(name: "An interesting Event")
}

Subscribing to the event

let subscription = Causality.bus.subscribe(MyEvents.interestingEvent) { message in
    print("A message from interestingEvent: \(message)")
}

Publish events

To publish/post an event of this type:

Causality.bus.publish(MyEvents.interestingEvent, 
    message: InterestingMessage(string: "Hello", number: 42))

To unsubsrcibe from an event

Causality.bus.unsubscribe(subscriptionId)

API Documentation

For more information visit our API reference.

Related Projects

• OpenCombine
• EventBus
• TopicEventBus
• SwiftEventBus
• EmitterKit

License

This library is licensed under Apache 2.0. The full license text is available in LICENSE.