Reactive Thinking in iOS Development - Pedro Piñera Buendía - Codemotion Amsterdam 2016
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In a world where Imperative Programming is the most used paradigm, Reactive comes up to make our code more reusable, robust, and stateless. Learn what Functional Reactive Programming means and how it could help you with problems you have to face daily in your projects. We’ll present basic concepts and practical examples for iOS developers that will help you to start thinking in streams, observers, .. and mix them with cool Swift functional concepts.
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Reactive Thinking in iOS Development - Pedro Piñera Buendía - Codemotion Amsterdam 2016
- 1. REACTIVE THINKING IN IOS DEVELOPMENT@PEPIBUMUR / @SAKY
- 2. WHO? @pepibumur iOS Developer at SoundCloud GitHub: pepibumur Twitter: pepibumur @saky iOS Developer at Letgo GitHub: isaacroldan Twitter: saky GitDo.io our spare time project
- 3. INDEX > Programming Paradigms > Reactive Libraries > Reactive Motivation > Reactive Thinking > Reactive Caveats > Conclusion
- 4. PARADIGMS !WAYS OF SEEING THE WORLD WHEN IT COMES TO PROGRAMMING
- 5. WIKIPEDIA Data-Driven, Declarative, Dynamic, End-User, Event-Driven, Expression-Oriented, Feature-Oriented, Function-level, Generic, Imperative, Inductive, Language Oriented, Metaprogramming, Non-Structured, Nondeterministic, Parallel computing, Point-free Style, Structured, Value- Level, Probabilistic
- 8. HOW SEQUENCE OF STEPS THAT HAPPEN IN ORDER
- 10. EXECUTION STATE(AKA SIDE EFFECT)
- 11. IMPERATIVE PROGRAMMING func userDidSearch(term: String) { let apiReults = api.search(term: term).execute() self.items = self.adaptResults(apiResults) self.tableView.reloadData() }
- 13. WHAT IT DOESN'T DESCRIBE THE CONTROL FLOW
- 14. HTML
- 15. HTML SQL
- 17. DECLARATIVE PROGRAMMING let predicate = NSPredicate(format: "name == %@", "Pedro") let regex = NSRegularExpression(pattern: ".+", options: 0)
- 18. REACTIVE PROGRAMMING DATA-FLOW PROGRAMMING (DESCRIBES THE STATE PROPAGATION) # THE INTRODUCTION TO REACTIVE PROGRAMMING THAT YOU'VE BEEN MISSING
- 20. REACTIVE LIBRARIES > RxSwift (ReactiveX) > ReactiveCocoa > BrightFutures > ReactKit > Bond > More and more... PromiseKit, Bolts...
- 21. WHAT LIBRARY SHOULD I USE? !
- 22. WHAT LIBRARY SHOULD I USE? ! DO I NEED A LIBRARY FOR THIS? !
- 23. SWIFT var userName: String { didSet { // React to changes in variables } }
- 24. SWIFT var userName: String { didSet { // React to changes in variables view.updateTitle(userName) } }
- 25. MOTIVATION !WHY SHOULD I STICK TO REACTIVE PROGRAMMING?
- 26. > Bindings > Composability > Threading
- 27. > Bindings > Composability > Threading
- 28. BINDING
- 29. UI BINDING
- 30. UI BINDING
- 31. UI BINDING
- 32. > Bindings > Composability > Threading
- 35. > Bindings > Composability > Threading
- 36. > Bindings > Composability > Threading (observer and execution)
- 37. THREADING
- 39. THINKING IN TERMS OF OBSERVABLESOR SIGNALS/PRODUCERS IN REACTIVECOCOA
- 42. OPERATIONS RxSwift Observable<String>.create { (observer) -> Disposable in observer.onNext("next value") observer.onCompleted() return NopDisposable.instance // For disposing the action } ReactiveCocoa SignalProducer<String>.create { (observer, disposable) in observer.sendNext("next value") observer.sendComplete() }
- 43. EXISTING PATTERNSRXSWIFT ▶︎ RXCOCOA (EXTENSIONS) REACTIVECOCOA ▶︎ DO IT YOURSELF
- 44. UIKIT let button = UIButton() button.rx_controlEvent(.TouchUpInside) .subscribeNext { _ in print("The button was tapped") }
- 45. NOTIFICATIONS NSNotificationCenter.defaultCenter() .rx_notification("my_notification", object: nil) .subscribeNext { notification // We got a notification }
- 46. DELEGATES self.tableView.rx_delegate // DelegateProxy .observe(#selector(UITableViewDelegate.tableView(_:didSelectRowAtIndexPath:))) .subscribeNext { (parameters) in // User did select cell at index path }
- 48. OBSERVABLE let tracksFetcher = api.fetchTracks // Background .asObservable()
- 49. ERROR HANDLING let tracksFetcher = api.fetchTracks // Background .asObservable() .retry(3) .catchErrorJustReturn([])
- 50. MAPPING let tracksFetcher = api.fetchTracks // Background .asObservable() .retry(3) .catchErrorJustReturn([]) .map(TrackEntity.mapper().map)
- 51. FILTERING let tracksFetcher = api.fetchTracks // Background .asObservable() .retry(3) .catchErrorJustReturn([]) .map(TrackEntity.mapper().map) .filter { $0.name.contains(query) }
- 52. FLATMAPPING let tracksFetcher = api.fetchTracks // Background .asObservable() .retry(3) .catchErrorJustReturn([]) .map(TrackEntity.mapper().map) .filter { $0.name.contains(query) } .flatMap { self.rx_trackImage(track: $0) }
- 53. OBSERVATION THREAD let tracksFetcher = api.fetchTracks // Background .asObservable() .retry(3) .catchErrorJustReturn([]) .map(TrackEntity.mapper().map) .filter { $0.name.contains(query) } .flatMap { self.rx_trackImage(track: $0) } .observeOn(MainScheduler.instance) // Main thread
- 54. LE IMPERATIVE WAY !" func fetchTracks(retry retry: Int = 0, retryLimit: Int, query: query, mapper: (AnyObject) -> Track, completion: ([UIImage], Error?) -> ()) { api.fetchTracksWithCompletion { (json, error) in if let _ = error where retry < retryLimit { fetchTracksWithRetry(retry: retry+1, retryLimit: retryLimit, query: query, mapper: mapper, completion: completion) } else if let error = error { completion([], error) } else if let json = json { guard let jsonArray = json as? [AnyObject] else { completion([], Error.InvalidResponse) return } let mappedTracks = jsonArray.map(mapper) let filteredTracks = mappedTracks.filter { $0.name.contains(query) } self.fetchImages(track: filteredTracks, completion: ([])) let trackImages = self.fetchImages(tracks: filteredTracks, completion: { (images, error) in dispatch_async(dispatch_get_main_queue(),{ if let error = error { completion([], error) return } completion(images, error) }) }) } } }
- 55. THROTTLING CLASSIC REACTIVE EXAMPLE func tracksFetcher(query: String) -> Observable<[TrackEntity]> searchTextField .rx_text.throttle(0.5, scheduler: MainScheduler.instance) .flatmap(tracksFetcher) .subscribeNext { tracks in // Yai! Tracks searched }
- 56. OTHER OPERATORS Combining / Skipping Values / Deferring / Concatenation / Take some values / Zipping
- 58. SUBSCRIBING observable subscribe { event switch (event) { case .Next(let value): print(value) case .Completed: print("completed") case .Error(let error): print("Error: (error)") } }
- 59. BIND CHANGES OVER THE TIME TO AN OBSERVABLEOBSERVABLE ▶ BINDING ▶ OBSERVER
- 60. BINDING To a Variable let myVariable: Variable<String> = Variable("") observable .bindTo(myVariable) print(myVariable.value) To UI observable .bindTo(label.rx_text)
- 62. ! CAVEATSBECAUSE YES... IT COULDN'T BE PERFECT
- 63. DEBUGGINGDEBUG OPERATOR IN RXSWIFT
- 64. let tracksFetcher = api.fetchTracks // Background .asObservable() .retry(3) .catchErrorJustReturn([]) .map(TrackEntity.mapper().map) .filter { $0.name.contains(query) } .flatMap { self.rx_trackImage(track: $0) } .observeOn(MainScheduler.instance) // Main thread
- 65. let tracksFetcher = api.fetchTracks // Background .asObservable .debug("after_fetch") // <-- Debugging probes .retry(3) .catchErrorJustReturn([]) .map(TrackEntity.mapper().map) .debug("mapped_results") // <-- Debugging probes .filter { $0.name.contains(query) } .flatMap { self.rx_trackImage(track: $0) } .observeOn(MainScheduler.instance) // Main thread
- 66. //let tracksFetcher = api.fetchTracks // Background // .asObservable .debug("after_fetch") // <-- Debugging probes // .retry(3) // .catchErrorJustReturn([]) // .map(TrackEntity.mapper().map) .debug("mapped_results") // <-- Debugging probes // .filter { $0.name.contains(query) } // .flatMap { self.rx_trackImage(track: $0) } // .observeOn(MainScheduler.instance) // Main thread
- 67. > [after_fetch] Next Event... // Downloaded tracks > [mapped_results] Error ... // Detected error after mapping > [...]
- 68. RETAIN CYCLES class IssuePresenter { var disposable: Disposable func fetch() { self.disposable = issueTitle .observable() .bindTo { self.titleLabel.rx_text } } }
- 69. UNSUBSCRIPTION YOU NEED TO TAKE CARE OF THE LIFECYCLE OF YOUR OBSERVABLES
- 70. UNSUBSCRIPTION title.asObservable().bindTo(field.rx_text) // RxSwift will show a warning
- 71. UNSUBSCRIPTION let titleDisposable = title.asObservable().bindTo(field.rx_text) titleDisposable.dispose()
- 72. UNSUBSCRIPTION let disposeBag = DisposeBag() title.asObservable() .bindTo(field.rx_text) .addDisposableTo(disposeBag) // The binding is active until the disposeBag is deallocated
- 73. CONCLUSIONS
- 75. DATA FLOW MANIPULATION BECOMES EASIER
- 76. BUT... !
- 77. YOU COUPLE YOUR PROJECT TO A LIBRARY !
- 78. REACTIVE CODE SPREADS LIKE A VIRUS !OVERREACTIVE ⚠
- 79. DEFINE REACTIVE DESIGN GUIDELINES AND STICK TO THEM
- 80. HAVE REACTIVE FUN !
- 81. REFERENCES > rxmarbles.com > RxSwift Community > RxSwift Repository > ReactiveCocoa
- 82. WE ARE HIRINGPEPI@SOUNDCLOUD.COM - ISAAC@LETGO.COM ❄ BERLIN - BARCELONA !
- 84. THANKSQUESTIONS? SLIDES HTTP://BIT.LY/1RFWLCI @SAKY - @PEPIBUMUR