Swift & ReactiveX – Asynchronous Event-Based Funsies with RxSwift

This is an introduction to reactive concepts using Swift specifically with ReactiveX’s implementation, RxSwift. ReactiveX is an API for asynchronous programming with observable streams originally implemented with .NET and LINQ. ReactiveX is a combination of the best ideas from the Observer pattern, the Iterator pattern, and functional programming.

You’ll learn about all the basic moving parts of RxSwift and why you want to use it in your application.

Original presented 23-Aug-2016 at 360iDev 2016 - Denver, CO.

Transcript

1. SWIFT & REACTIVEX Asynchronous Event-Based Funsies with RxSwift
2. WHO I AM ➤ Aaron Douglas ➤ Milwaukee, WI USA ➤ Mobile Maker for Automattic (WordPress.com) ➤ Remote full time 3+ years ➤ @astralbodies
3. REACTIVE?
 FUNCTIONAL?
 MEH?
4. FUNCTIONAL & REACTIVE PROGRAMMING ➤ Reactive Programming ➤ Asynchronous Data Flow ➤ Functional Programming ➤ Map, Reduce, Filter ➤ Avoiding State ➤ Immutable Data ➤ Declarative Paradigm - logic of computation rather than describing flow ➤ Implementations - ReactiveCocoa/RAC, RxSwift
5. WHAT IS RXSWIFT?
6. WHAT IS RXSWIFT? ➤ Based on ReactiveX ➤ Many different ports: Java, JavaScript, .NET, Scala, Clojure, Swift, Kotlin, PHP , … ➤ Extends the Observer Pattern ➤ Related to Iterable Pattern ➤ Swift itself provides some protocols with equivalence ➤ SequenceType ➤ GeneratorType
7. OBSERVER PATTERN
8. NSNOTIFICATIONCENTER NSNotificationCenter .defaultCenter() .addObserver(self, selector:"downloadImage:", name: "BLDownloadImageNotification", object: nil) NSNotificationCenter .defaultCenter() .postNotificationName("BLDownloadImageNotification", object: self, userInfo: ["imageView": coverImage, "coverUrl": albumCover])
9. OBSERVER PATTERN 9
10. ITERATOR PATTERN
11. ITERATOR PATTERN
12. GENERATORS, SEQUENCES, OH MY!
13. GENERATORS public protocol GeneratorType { associatedtype Element public mutating func next() -> Self.Element? }
14. GENERATORS class CountdownGenerator: GeneratorType { typealias Element = Int var element: Element init<T>(array: [T]) { self.element = array.count } func next() -> Element? { guard element > 0 else { return nil } element -= 1 return element } } let xs = ["A", "B", "C"] let generator = CountdownGenerator(array: xs) while let i = generator.next() { print("Element \(i) of the array is \(xs[i])") } Element 2 of the array is C Element 1 of the array is B Element 0 of the array is A
15. SEQUENCES public protocol SequenceType { associatedtype Generator : GeneratorType public func generate() -> Self.Generator }
16. SEQUENCES class ReverseSequence<T>: SequenceType { var array: [T] init(array: [T]) { self.array = array } func generate() -> CountdownGenerator { return CountdownGenerator(array: array) } } let reverseSequence = ReverseSequence(array: xs) let reverseGenerator = reverseSequence.generate() while let i = reverseGenerator.next() { print("Index \(i) is \(xs[i])") } for i in ReverseSequence(array: xs) { print("Index \(i) is \(xs[i])") } Index 2 is C Index 1 is B Index 0 is A Index 2 is C Index 1 is B Index 0 is A
17. OBSERVABLES
18. OBSERVERTYPE public protocol ObserverType { associatedtype E func on(event: Event<E>) } public enum Event<Element> { case Next(Element) case Error(ErrorType) case Completed }
19. OBSERVABLETYPE public protocol ObservableType : ObservableConvertibleType { associatedtype E func subscribe<O: ObserverType where O.E == E>(observer: O) -> Disposable } public protocol ObservableConvertibleType { associatedtype E func asObservable() -> Observable<E> }
20. VISUALIZATIONS OF SEQUENCES --1--2--3--4--5--6--| // terminates normally --a--b--a--a--a---d---X // terminates with error ---tap-tap-------tap---> // infinite; never ends
21. MAKING AN OBSERVABLE let disposeBag = DisposeBag() Observable.just("X") .subscribe { event in print(event) } .addDisposableTo(disposeBag)
22. MAKING AN OBSERVABLE let disposeBag = DisposeBag() Observable.of("W", "X", "Y", "X") .subscribeNext { element in print(element) } .addDisposableTo(disposeBag)
23. MAKING AN OBSERVABLE let disposeBag = DisposeBag() ["W", "X", "Y", "Z"].toObservable() .subscribeNext { print($0) } .addDisposableTo(disposeBag)
24. SUBSCRIBING someObservable.subscribe( onNext: { print("Element: ", $0) }, onError: { print("Error: ", $0) }, onCompleted: { print("Completed") }, onDisposed: { print("Disposed") } ) someObservable .subscribeNext { print("Element: ", $0) }
25. OPERATORS
27. MAP
28. MAP let disposeBag = DisposeBag() Observable.of(1, 2, 3) .map { $0 * 10 } .subscribeNext { print($0) } .addDisposableTo(disposeBag) --- 10 20 30
29. FILTER
30. FILTER let disposeBag = DisposeBag() Observable.of(2, 30, 22, 5, 60, 1) .filter { $0 > 10 } .subscribeNext { print($0) } .addDisposableTo(disposeBag) --- 30 22 60
31. SCAN
32. SCAN let disposeBag = DisposeBag() Observable.of(1, 2, 3, 4, 5) .scan(0) { aggregateValue, newValue in aggregateValue + newValue } .subscribeNext { print($0) } .addDisposableTo(disposeBag) --- 1 3 6 10 15
33. MERGE
34. MERGE let disposeBag = DisposeBag() let subject1 = PublishSubject<String>() let subject2 = PublishSubject<String>() Observable.of(subject1, subject2) .merge() .subscribeNext { print($0) } .addDisposableTo(disposeBag) subject1.onNext("20") subject1.onNext("40") subject1.onNext("60") subject2.onNext("1") subject1.onNext("80") subject1.onNext("100") subject2.onNext("1") 20 40 60 1 80 100 1
35. RXMARBLES.COM
36. DISPOSING
37. .dispose()
38. .addDisposableTo(disposeBag)
39. COCOA + RXSWIFT
40. BINDINGS totCountStepper .rx_value .subscribeNext { value in self.totalNumberOfTots.value = Int(value) } .addDisposableTo(disposeBag)
41. BINDINGS ➤ NSTextStorage ➤ UIActivityIndicatorView ➤ UIAlertAction ➤ UIApplication ➤ UIBarButtonItem ➤ UIButton ➤ UICollectionView ➤ UIControl ➤ UIDatePicker ➤ UIGestureRecognizer ➤ UIImagePickerController ➤ UIImageView ➤ UILabel ➤ UINavigationItem ➤ UIPageControl ➤ UIPickerView ➤ UIProgressView ➤ UIRefreshControl ➤ UIScrollView ➤ UISearchBar ➤ UISearchController ➤ UISegmentedControl ➤ UISlider ➤ UIStepper ➤ UISwitch ➤ UITabBar ➤ UITabBarItem ➤ UITableView ➤ UITextField ➤ UITextView ➤ UIView ➤ UIViewController
42. AN EXAMPLE
43. TATER TOT TIMER
44. RXSWIFT IN THE WILD
45. WHERE TO LEARN MORE
46. WHERE TO LEARN MORE ➤ ReactiveX RxSwift main repo ➤ https://github.com/ReactiveX/RxSwift/ ➤ FRP iOS Learning Resources ➤ https://gist.github.com/JaviLorbada/4a7bd6129275ebefd5a6 ➤ Functional Reactive Programming with RxSwift ➤ https://realm.io/news/slug-max-alexander-functional-reactive-rxswift/ ➤ RxSwift Slack ➤ http://rxswift-slack.herokuapp.com/
47. AARON DOUGLAS @astralbodies http://astralbodi.es