Swen - An Event Bus written in Swift
- Typesafe events
- Pass custom objects
- Threadsafe
- Sticky events
- Fast and small
Getting started
Swen is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod "Swen"Example
To run the example project, clone the repo, and run pod install from the Example directory first.
Requirements
- iOS 9.0+ / macOS 10.10+ / tvOS 9.0+ / watchOS 2.0+
- Xcode 8.1+
- Swift 3.0+
Usage
import Swen
struct TestEvent: Event {
let name: String
}
class TestViewController: UIViewController {
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
//register for incoming events
Swen<TestEvent>.register(self) { event in
print(event.name)
}
//post event
Swen.post(TestEvent(name: "Sixt"))
}
override func viewDidDisappear(_ animated: Bool) {
super.viewDidDisappear(animated)
//unregister from events
Swen<TestEvent>.unregister(self)
}
}Register on different threads
// Registers on the main thread
Swen<Event>.register(_ observer: AnyObject, handler: (_ event: Event) -> Void)
// Registers on background queue
Swen<Event>.registerOnBackground(_ observer: AnyObject, handler: (_ event: Event) -> Void)
// Registers the closure on a specific queue
Swen<Event>.register(_ observer: AnyObject, onQueue queue: OperationQueue, handler: (_ event: Event) -> Void)Sticky events
Sometimes events carry information that is not only important for that one moment but needs to be kept around longer. For these cases sticky events come in handy. They behave the same as normal events with two further additions. First you can query them by:
struct TestStickyEvent: StickyEvent {
let name: String
}
print(Swen<TestStickyEvent>.sticky()?.name)Important: The return sticky is optional, because the event may not be posted yet!
The second additions is that if you register for a sticky event and one was already posted before. It will immediately trigger the registered closure
class TestViewController: UIViewController {
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
//post event
Swen.post(TestStickyEvent(name: "Stick it"))
//register for incoming events
Swen<TestStickyEvent>.register(self) { event in
print(event.name)
}
}
}System Events
To use System Events, write wrapper for interest NSNotifications:
public struct SystemEvents {
struct ApplicationWillEnterForeground: Event {
}
static func register(storage: SwenStorage = .defaultStorage) {
let center = NotificationCenter.default
center.addObserver(forName: .UIApplicationWillEnterForeground, object: nil, queue: nil) { _ in
Swen.post(ApplicationWillEnterForeground(), in: storage)
}
}
}Dependency Injection
To encapsulate test cases from production code and from each other, we suggest to use Dependency Injection and Storage mechanism:
class TestViewController: UIViewController {
var swenStorage = SwenStorage()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
//register for incoming events in custom storage
Swen<TestEvent>.register(self, in: swenStorage) { event in
print(event.name)
}
//register for incoming events in default storage
Swen<TestEvent>.register(self) { event in
print(event.name)
}
//post event in custom storage
Swen.post(TestEvent(name: "Sixt, custom storage"), in: swenStorage)
//post event in default storage
Swen.post(TestEvent(name: "Sixt, default storage"))
}
}Performance
One of the other main benefits of using Swen is the significant performance increase over NSNotificationCenter
| Performance Test | NSNotificationCenter | SwiftBus |
|---|---|---|
| Perform 10ˆ6 Events to 1 receiver | 6.54s | 2.61s |
| Perform 10ˆ3 Events to 10ˆ3 receivers | 14.42s | 11.15s |
Author
- e-Sixt, sixtlabs@sixt.com
Contributors:
- Dmitry Poznukhov, dmitry.poznukhov@sixt.com
- Franz Busch, franz-joseph.busch@sixt.com
- Dedicated to Sven Röder
License
Swen is available under the MIT license. See the LICENSE file for more info.
