Signals
Signals is a library for creating and observing events. It replaces delegates, actions and NSNotificationCenter with something much more powerful and elegant.
Features
- Attach-and-forget observation
- Type-safety
- Filtered observation
- Delayed and queued observation
- Comprehensive Unit Test Coverage
Requirements
- iOS 7.0 / watchOS 2.0 / Mac OS X 10.9
- Swift 4.2
Installation
To use Signals with a project targeting iOS 7, simply copy Signals.swift into your project.
CocoaPods
To integrate Signals into your project add the following to your Podfile:
platform :ios, '8.0'
use_frameworks!
pod 'Signals', '~> 6.0'
Carthage
To integrate Signals into your project using Carthage add the following to your Cartfile:
github "artman/Signals" ~> 6.0
Swift Package Manager
To integrate Signals into your project using SwiftPM add the following to your Package.swift:
dependencies: [
.package(url: "https://github.com/artman/Signals", from: "6.0.0"),
],
Quick start
Make events on a class observable by creating one or more signals:
class NetworkLoader {
// Creates a number of signals that can be subscribed to
let onData = Signal<(data:NSData, error:NSError)>()
let onProgress = Signal<Float>()
...
func receivedData(receivedData:NSData, receivedError:NSError) {
// Whenever appropriate, fire off any of the signals
self.onProgress.fire(1.0)
self.onData.fire((data:receivedData, error:receivedError))
}
}
Subscribe to these signals from elsewhere in your application
let networkLoader = NetworkLoader("http://artman.fi")
networkLoader.onProgress.subscribe(with: self) { (progress) in
print("Loading progress: \(progress*100)%")
}
networkLoader.onData.subscribe(with: self) { (data, error) in
// Do something with the data
}
Adding subscriptions to Signals is an attach-and-forget operation. If the subscribing object is deallocated, the Signal cancels the subscription, so you don't need to explicitly manage the cancellation of your subsciptions.
Singals aren't restricted to one subscriber. Multiple objects can subscribe to the same Signal.
You can also subscribe to events after they have occurred:
networkLoader.onProgress.subscribePast(with: self) { (progress) in
// This will immediately fire with last progress that was reported
// by the onProgress signal
println("Loading progress: \(progress*100)%")
}
Advanced topics
Signal subscriptions can apply filters:
networkLoader.onProgress.subscribe(with: self) { (progress) in
// This fires when progress is done
}.filter { $0 == 1.0 }
You can sample up subscriptions to throttle how often you're subscription is executed, regardless how often the Signal fires:
networkLoader.onProgress.subscribe(with: self) { (progress) in
// Executed once per second while progress changes
}.sample(every: 1.0)
By default, a subscription executes synchronously on the thread that fires the Signal. To change the default behaviour, you can use the dispatchOnQueue method to define the dispatch queue:
networkLoader.onProgress.subscribe(with: self) { (progress) in
// This fires on the main queue
}.dispatchOnQueue(DispatchQueue.main)
If you don't like the double quotes when you fire signals that take tuples, you can use the custom => operator to fire the data:
// If you don't like the double quotes when firing signals that have tuples
self.onData.fire((data:receivedData, error:receivedError))
// You can use the => operator to fire the signal
self.onData => (data:receivedData, error:receivedError)
// Also works for signals without tuples
self.onProgress => 1.0
Replacing actions
Signals extends all classes that extend from UIControl (not available on OS X) and lets you use Signals to listen to control events for increased code locality.
let button = UIButton()
button.onTouchUpInside.observe(with: self) {
// Handle the touch
}
let slider = UISlider()
slider.onValueChanged.observe(with: self) {
// Handle value change
}
Replacing delegates
Signals is simple and modern and greatly reduce the amount of boilerplate that is required to set up delegation.
Would you rather implement a callback using a delegate:
- Create a protocol that defines what is delegated
- Create a delegate property on the class that wants to provide delegation
- Mark each class that wants to become a delegate as comforming to the delegate protocol
- Implement the delegate methods on the class that want to become a delegate
- Set the delegate property to become a delegate of the instance
- Check that your delegate implements each delegate method before invoking it
Or do the same thing with Signals:
- Create a Signal for the class that wants to provide an event
- Subscribe to the Signal
Replace NotificationCenter
When your team of engineers grows, NotificationCenter quickly becomes an anti-pattern. Global notifications with implicit data and no compiler safety easily make your code error-prone and hard to maintain and refactor.
Replacing NotificationCenter with Signals will give you strong type safety enforced by the compiler that will help you maintain your code no matter how fast you move.
Communication
- If you found a bug, open an issue or submit a fix via a pull request.
- If you have a feature request, open an issue or submit a implementation via a pull request or hit me up on Twitter @artman
- If you want to contribute, submit a pull request onto the master branch.
License
Signals is released under an MIT license. See the LICENSE file for more information
2.2k Jan 1, 2023
759 Dec 2, 2022
2.5k Dec 28, 2022
160 Dec 25, 2022
35 Dec 29, 2022
3 May 18, 2022
1.9k Dec 20, 2022
2k Dec 30, 2022
324 Dec 17, 2022
7 Jun 11, 2022
108 Nov 11, 2022
1k Dec 19, 2022
1.2k Dec 9, 2022
708 Jun 29, 2022
4 Nov 2, 2022
13 Oct 28, 2022
493 Dec 25, 2022
261 Dec 15, 2022