A gentle introduction to RxSwift

https://github.com/gonzalezreal/rxswift-gentle-introduction

Swift has prompted the adoption of functional programming idioms and styles among app developers. If you have been running from this “functional weirdness” it is time to stop and embrace it.

Reactive Functional Programming is one of these idioms, and it is becoming quite popular thanks to ReactiveX (also known as Rx) and its Swift incarnation, RxSwift.

Transcript

1. RxSwift A gentle introduction “RxSwift, A gentle introduction” - Guille González @gonzalezreal
2. Guille González @gonzalezreal “RxSwift, A gentle introduction” - Guille González @gonzalezreal
3. http://reactivex.io “RxSwift, A gentle introduction” - Guille González @gonzalezreal
4. Observer on steroids “RxSwift, A gentle introduction” - Guille González @gonzalezreal
5. Taps, keyboard events, timers, GPS events, web service responses ↓ UI update, data written to disk, API request, etc. “RxSwift, A gentle introduction” - Guille González @gonzalezreal
6. Asynchronous Events in Cocoa → Target-Action → NSNotificationCenter → Key-Value Observing → Delegates → Callback Closures “RxSwift, A gentle introduction” - Guille González @gonzalezreal
7. Observable<Element> “RxSwift, A gentle introduction” - Guille González @gonzalezreal
8. --1--2--3--4--5-|---> --a--b--b--a--✕-----> ---tap-tap----tap---> ---JSON-|-----------> -|------------------> -✕------------------> “RxSwift, A gentle introduction” - Guille González @gonzalezreal
9. enum Event<Element> { case Next(Element) case Error(ErrorType) case Completed } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
10. --Next("a")--Next("b")--Error(diskError)-> -----Next---Next-------Next--------------> ---Next(json)-Completed------------------> “RxSwift, A gentle introduction” - Guille González @gonzalezreal
11. Creating Observables → Observable.empty() → Observable.just("!") → Observable.of("!", """, "⚽") → Observable.error(Error.CouldNotDecodeJSON) “RxSwift, A gentle introduction” - Guille González @gonzalezreal
12. Creating Observables let o = Observable.create { observer in observer.on(.Next("! world!")) observer.on(.Completed) return NopDisposable.instance } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
13. If a tree falls in a forest and no one is around to hear it, does it make a sound? — George Berkeley “RxSwift, A gentle introduction” - Guille González @gonzalezreal
14. ┌─────────────────────────────────────┬─────────────────────────────────────┐ │ Hot Observables │ Cold observables │ ├─────────────────────────────────────┼─────────────────────────────────────┤ │Use resources even when there are no │Don't use resources until there is a │ │subscribers. │subscriber. │ ├─────────────────────────────────────┼─────────────────────────────────────┤ │Resources usually shared between all │Resources usually allocated per │ │the subscribers. │subscriber. │ ├─────────────────────────────────────┼─────────────────────────────────────┤ │Usually stateful. │Usually stateless. │ ├─────────────────────────────────────┼─────────────────────────────────────┤ │UI controls, taps, sensors, etc. │HTTP request, async operations, etc. │ └─────────────────────────────────────┴─────────────────────────────────────┘ “RxSwift, A gentle introduction” - Guille González @gonzalezreal
15. Observers protocol ObservableType { func subscribe(on: (event: Event) -> Void) -> Disposable } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
16. Observers Observable.create { observer in observer.onNext("! world!") observer.onCompleted() return NopDisposable.instance }.subscribe { event in print(event) } // outputs: // Next(! world!) // Completed “RxSwift, A gentle introduction” - Guille González @gonzalezreal
17. Observers Observable.create { observer in observer.onNext("! world!") observer.onCompleted() return NopDisposable.instance }.subscribeNext { text in print(text) } // outputs: // ! world! “RxSwift, A gentle introduction” - Guille González @gonzalezreal
18. Disposables let appleWeb = Observable.create { observer in let task = session.dataTaskWithURL(appleURL) { data, response, error in if let data = data { observer.onNext(data) observer.onCompleted() } else { observer.onError(error ?? Error.UnknownError) } } task.resume() return AnonymousDisposable { task.cancel() } } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
19. Dispose Bags self.disposeBag = DisposeBag() ... appleWeb.subscribeNext { data in print(data) }.addDisposableTo(disposeBag) “RxSwift, A gentle introduction” - Guille González @gonzalezreal
20. Operators → map → flatMap → filter → throttle → merge → combineLatest → and many more... “RxSwift, A gentle introduction” - Guille González @gonzalezreal
21. map & flatMap struct Country { let name: String let borders: [String] } protocol CountriesAPI { func countryWithName(name: String) -> Observable<Country> func countriesWithCodes(codes: [String]) -> Observable<[Country]> } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
22. map & flatMap myAPI.countryWithName("spain") .flatMap { country in myAPI.countriesWithCodes(country.borders) } .map { countries in countries.map { $0.name } } .subscribeNext { countryNames in print(countryNames) } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
23. Observable chaining is similar to Optional chaining: let cell = UITableViewCell(style: .Default, reuseIdentifier: nil) let maybeSize = cell.imageView?.image?.size let maybeSize2 = cell.imageView.flatMap { $0.image }.flatMap { $0.size } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
24. observeOn myAPI.countryWithName("spain") .flatMap { country in myAPI.countriesWithCodes(country.borders) } .map { countries in countries.map { $0.name } } .observeOn(MainScheduler.instance) .subscribeNext { countryNames in // Main thread, all good } “RxSwift, A gentle introduction” - Guille González @gonzalezreal
25. “RxSwift, A gentle introduction” - Guille González @gonzalezreal
26. throttle let results = searchBar.rx_text .throttle(0.3, scheduler: MainScheduler.instance) .flatMapLatest { query in if query.isEmpty { return Observable.just([]) } return searchShows(query) } .observeOn(MainScheduler.instance) .shareReplay(1) “RxSwift, A gentle introduction” - Guille González @gonzalezreal
27. combineLatest Observable.combineLatest(emailField.rx_text, passwordField.rx_text) { email, password in return email.characters.count > 0 && password.characters.count > 0 } .bindTo(sendButton.rx_enabled) .addDisposableTo(disposeBag) “RxSwift, A gentle introduction” - Guille González @gonzalezreal
28. Follow-up Resources → reactivex.io → rxmarbles.com → github.com/ReactiveX/RxSwift → tinyurl.com/consuming-web-services “RxSwift, A gentle introduction” - Guille González @gonzalezreal
29. Questions? Comments? “RxSwift, A gentle introduction” - Guille González @gonzalezreal