Reactive Thinking in iOS Development

Transcript

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

6. IMPERATIVE PROGRAMMING DECLARATIVE PROGRAMMING

7. IMPERATIVE PROGRAMMING DECLARATIVE PROGRAMMING

8. HOW SEQUENCE OF STEPS THAT HAPPEN IN ORDER

9. NATURAL WAY TO PROGRAM

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() }

12. IMPERATIVE PROGRAMMING DECLARATIVE PROGRAMMING

13. WHAT IT DOESN'T DESCRIBE THE CONTROL FLOW

14. HTML

15. HTML SQL

16. HTML SQL REACTIVE PROGRAMMING

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

19. FUNCTIONAL REACTIVE PROGRAMMING (AKA FRP)

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

33. None
34. None

35. > Bindings > Composability > Threading

36. > Bindings > Composability > Threading (observer and execution)

37. THREADING

38. REACTIVE THINKING !

39. THINKING IN TERMS OF OBSERVABLES OR SIGNALS/PRODUCERS IN REACTIVECOCOA

40. ACTIONS CAN BE OBSERVED HOW? !

41. .NEXT(T) .ERROR(ERRORTYPE) .COMPLETE

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 PATTERNS RXSWIFT ▶︎ 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 }

47. PLAYING ! WITH OBSERVABLES

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

57. OBSERVING ! EVENTS

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 OBSERVABLE OBSERVABLE ▶

    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)
61. None

62. ! CAVEATS BECAUSE YES... IT COULDN'T BE PERFECT

63. DEBUGGING DEBUG 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

74. PREVENTS STATEFUL CODE

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 HIRING [email protected] - [email protected] ❄ BERLIN - BARCELONA

    !
83. None

84. THANKS QUESTIONS? SLIDES HTTP://BIT.LY/1RFWLCI @SAKY - @PEPIBUMUR