8 uses of RxSwift

These are the slides of the talk I gave at Swift Toulouse Meetup. I explore (almost) 8 ways to use RxSwift. From the very basics like networking and binding to more personal tips or examples of my own.

Transcript

1. 8 uses of RxSwift
2. The 5th is amazing
3. → I'm Jérôme Alves → Lead iOS Developer @ Heetch → @jegnux on Twitter, Github, Slack, etc...
4. #1 Networking
5. searchBar.rx .text.orEmpty .throttle(0.3, scheduler: MainScheduler.instance) .distinctUntilChanged() .flatMapLatest { query -> Observable<[Repository]> in if query.isEmpty { return .just([]) } let request = APIClient.makeSearchRequest(query: query) return URLSession.shared.rx.json(request) } .observeOn(MainScheduler.instance) ...
6. ---(x) --(x) --(x)-----------------(x) --(x)----------------> .throttle(0.5, scheduler: MainScheduler.instance) ---(x)----(x)(x)-----------------(x)-----(x)-------------> .debounce(0.5, scheduler: MainScheduler.instance) --------------------(x)------------------(x)------------->
7. ---(a) --(b) --(b) --(c)----------(c) --(d)------------------> .distinctUntilChanged() ---(a) --(b)-------(c)---------------(d)------------------>
8. a: |---------(tap)-----(tap)-------------------------> b: |-(GET)--------(response) ---> a.flatMapLatest(b) |---------(GET)-----(GET)--------(response)-------->
9. Other useful operators for networking: .flatMap( ...) .flatMapFirst( ...) .catchError( ...) .catchErrorJustReturn( ...) .catchErrorJustComplete() .retry( ...) .observeOn( ...) ...
10. reactivex.io rxmarbles.com rxviz.com
11. #2 Binding
12. viewModel.address .bind(to: addressLabel.rx.text) .disposed(by: disposeBag)
13. viewModel.address .map { $0.isEmpty } .bind(to: addressLabel.rx.isHidden) .disposed(by: disposeBag)
14. #3 Unifying
15. How many patterns in Cocoa to be notified of a change?
16. → delegation → target / action → notifications → completion blocks → key-value observing → subclassing
17. SUBCLASSING?
18. UIViewController.viewDidLoad() UIViewController.viewWillAppear(_ animated:) UIViewController.viewDidAppear(_ animated:) UIViewController.viewWillDisappear(_ animated:) UIViewController.viewDidDisappear(_ animated:) UIViewController.willMove(toParentViewController:) UIViewController.didMove(toParentViewController:)
19. UIViewController.viewLayoutMarginsDidChange() UIViewController.viewSafeAreaInsetsDidChange() UIViewController.viewWillLayoutSubviews() UIViewController.viewDidLayoutSubviews()
20. UIView.layoutMarginsDidChange() UIView.safeAreaInsetsDidChange() UIView.tintColorDidChange() UIView.didAddSubview(_:) UIView.willRemoveSubview(_:)
21. RxSwift and RxCocoa provide an unified API for all these patterns
22. Story time
23. As a user, when keyboard appears to fill my address, display an auto-fill button. When I tap on the button, fetch device location, then I reverse geocode location coordinate to an address which I use to fill the textview.
24. → keyboard appears → Notification → tap → Target / Action → fetch device location → Delegation → reverse geocode → Completion block
25. → NotificationCenter.default.rx.notification(_:) → tap → Target / Action → fetch device location → Delegation → reverse geocode → Completion block
26. → NotificationCenter.default.rx.notification(_:) → autofillButton.rx.tap → fetch device location → Delegation → reverse geocode → Completion block
27. → NotificationCenter.default.rx.notification(_:) → autofillButton.rx.tap → locationManager.rx.location → reverse geocode → Completion block
28. → NotificationCenter.default.rx.notification(_:) → autofillButton.rx.tap → locationManager.rx.location → geocoder.rx.reverseGeocode(coordinate:)
29. NotificationCenter.default.rx .notification(.UIKeyboardWillShow) .do(onNext: { autofillButton.isHidden = false }) .flatMapLatest { _ in locationManager.rx.location } .flatMapLatest { location in geocoder.rx.reverseGeocode(coordinate: location) } .sample(autofillButton.rx.tap) .bind(to: addressTextField.rx.text)
30. #4 Triggering
31. As an user, I want my feed reloaded... → when the view appears → when I'm back from background → every 60 seconds → when I tap on refresh button
32. When the view appears self.rx.methodInvoked( #selector(viewDidAppear) ) -> Observable<[Any]>
33. When I'm back from background NotificationCenter.default.rx.notification( .UIApplicationWillEnterForeground ) -> Observable<Notification>
34. Every 60 seconds Observable<Int>.interval( 60, scheduler: MainScheduler.instance ) -> Observable<Int>
35. When I tap on refresh button refreshButton.rx.tap -> ControlEvent<Void>
36. Merge all the Observables
37. Observable.merge( self.rx.methodInvoked(#selector(viewDidAppear)), NotificationCenter.default.rx.notification(.UIApplicationWillEnterForeground), Observable<Int>.interval(60, scheduler: MainScheduler.instance), refreshButton.rx.tap ) .subscribe(onNext: { _ in self.viewModel.reloadData() })
38. typealias Trigger = Observable<Void> extension ObservableType { func trigger() -> Trigger { return map { _ in () } } }
39. Observable.merge( self.rx.methodInvoked(#selector(viewDidAppear)).trigger(), NotificationCenter.default.rx.notification(.UIApplicationWillEnterForeground).trigger(), Observable<Int>.interval(60, scheduler: MainScheduler.instance).trigger(), refreshButton.rx.tap.trigger() ) .subscribe(onNext: { self.viewModel.reloadData() })
40. #5 Moving
42. Thanks to #unifying and #triggering it's easier to move away some code.
43. Analytics
44. Part 1 The old way
45. // FeedViewController var didAppearDate: Date? func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) // ... Analytics.track(.feedDidAppear) didAppearDate = Date() }
46. // FeedViewController func viewWillDisappear(_ animated: Bool) { super.viewWilDisappear(animated) // ... Analytics.track(.feedWillDisappear) if let date = didAppearDate { let duration = abs(date.timeIntervalSinceNow) Analytics.track(.feedAppearanceDuration, value: duration) } }
47. Part 2 The new, beautiful, shiny, elegant, reactive way
48. final class FeedAnalytics { init(feed: FeedViewController) { // ... } }
49. // FeedAnalytics.init(feed: FeedViewController) feed.rx .methodInvoked(#selector(viewDidAppear)) .subscribe(onNext: { _ in Analytics.track(.feedDidAppear) }) .disposed(by: feed.rx.disposeBag)
50. // FeedAnalytics.init(feed: FeedViewController) feed.rx .methodInvoked(#selector(viewWillDisappear)) .subscribe(onNext: { _ in Analytics.track(.feedWillDisappear) }) .disposed(by: feed.rx.disposeBag)
51. // FeedAnalytics.init(feed: FeedViewController) feed.rx .methodInvoked(#selector(viewDidAppear)) .map { _ in Date() } .flatMapLatest { [unowned feed] date in feed.rx .methodInvoked(#selector(viewWillDisappear)) .map { abs(date.timeIntervalSinceNow) } } .subscribe(onNext: { duration in Analytics.track(.feedAppearanceDuration, value: duration) }) .disposed(by: feed.rx.disposeBag)
52. let feed = FeedViewController() let feedAnalytics = FeedAnalytics(feed)
53. #6 Featuring
55. It's an expressive way to add features to your screens.
56. public struct Feature<T> { private let factory: (T) -> Disposable public init(_ factory: @escaping (T) -> Disposable) { self.factory = factory } public func install(in element: T, disposedBy disposeBag: DisposeBag) { factory(element).disposed(by: disposeBag) } }
57. extension UIViewController { public func addFeature(_ feature: Feature, disposeBag: DisposeBag) { feature.install(in: self, disposedBy: disposeBag) } }
58. extension UIViewController { public func addViewFeature(_ feature: Feature, disposeBag: DisposeBag) { if isViewLoaded { feature.install(in: self, disposedBy: disposeBag) return } rx.methodInvoked(#selector(UIViewController.viewDidLoad)) .take(1) .subscribe(onNext: { [unowned self] _ in feature.install(in: self, disposedBy: disposeBag) }) .disposed(by: disposeBag) } }
59. Examples
60. Shake to reload
61. protocol Reloadable : class { func reloadData() }
62. extension Feature where T : UIResponder & Reloadable { static var shakeToReload: Feature { return Feature { element in // ... } } }
63. return element.rx .methodInvoked(#selector(UIResponder.motionBegan(_:with:))) .filter { $0.first as! UIEventSubtype == .motionShake } .subscribe(onNext: { [weak element] _ in element ?.reloadData() })
64. let feed = FeedViewController() feed.addFeature(.shakeToReload)
65. Scroll to top with undo
66. http: //elegantswift.com
67. let feed = FeedViewController() feed.addFeature( .scrollToTop( scrollView: feed.collectionView, events: .statusBarTapped, .tabBarItemTapped ) )
68. #7 Stubbing
69. typealias Coordinate = CLLocationCoordinate2D class MapViewModel { init(userLocation: Observable<Coordinate>) { // ... } }
70. func locationStub(from source: Coordinate, to destination: Coordinate) -> Observable<Coordinate> { let coordinates = MKDirectionsRequest.rx .routes(from: source, to: destination, transportType: .walking) .map { $0.first ?.polyline } .unwrap() .map { polyline in let buffer = UnsafeBufferPointer(start: polyline.points(), count: polyline.pointCount) return Array(buffer).map(MKCoordinateForMapPoint) } .flatMap { Observable.from($0) } let trigger = Observable<Int>.interval(1, scheduler: MainScheduler.instance) return Observable.zip(coordinates, trigger, resultSelector: { $0 }) }
71. let viewModel = MapViewModel( userLocation: locationStub(from: a, to: b) )
72. #8 Drinking
73. Observable<Int>.interval(60*30, scheduler: EveningScheduler.instance) .map { Beer() } .takeUntil( self.bloodAlcoholLevel.filter { $0 < authorizedBloodAlcoholLevel } ) .subscribe(onNext: { drink($0) }) .disposed(by: wallet)
74. Thanks