Combine Overview

2019/08/05 Combineゴリゴリキャッチアップ会

Transcript

1. Combine Overview CombineΰϦΰϦΩϟονΞοϓձ Daiki Matsudate @d_date iOS Developer
2. Daiki Matsudate • Tokyo, Japan • iOS Developer from iOS 4 • Independent Developer • @d_date • Sushi
3. March, 18 - 20th, 2020 https://www.tryswift.co/
4. A unified, declarative API for 
 processing values over time
5. Why Reactive Programing?
6. Why Reactive Programing? • ෳ਺ͷඇಉظ (Asynchronous) ͳλεΫΛͲ͏ѻ͏͔ • Ͳ͏ѻ͏͔ • Ͳͷॱ൪Ͱʁ • ௚ྻ / ฒྻ? • ్தͰΤϥʔ͕ൃੜͨ͠Βʁ
7. Reactive Programing
8. Reactive Programming • Observer Pattern • ΠϕϯτͷൃՐΛϋϯυϦϯά͍ͨ͠ͱ͜ΖͰ؂ࢹ͢Δ • Operators • ΠϕϯτΛՃ޻͢Δ • Open Source • RxSwift / Reactive Swift
9. https://twitter.com/diegopetrucci/status/1135655480825655297
10. Combine
11. Combine • Declarative Swift API • ඇಉظͳΠϕϯτΛܕͱͯ͠දݱ • ଟछଟ༷ͳԋࢉࢠͰΠϕϯτΛϋϯυϦϯά • Reactive Framework by Apple
12. Publisher
13. Publisher • Value΍ErrorΛੜ੒͢Δ • ొ࿥͞ΕͨSubscriberʹValue΍ErrorΛૹ৴͢Δ
14. public protocol Publisher { /// The kind of values published by this publisher. associatedtype Output /// The kind of errors this publisher might publish. /// Use `Never` if this `Publisher` does not publish errors. associatedtype Failure : Error /// This function is called to attach the specified `Subscriber` to this `Publisher` by `subscribe(_:)` func receive<S>(subscriber: S) where S : Subscriber, Self.Failure == S.Failure, Self.Output == S.Input } Publisher
15. @Published @propertyWrapper public struct Published<Value> { /// Initialize the storage of the Published property as well as the corresponding `Publisher`. public init(initialValue: Value) public class Publisher : Publisher { /// The kind of values published by this publisher. public typealias Output = Value /// The kind of errors this publisher might publish. /// /// Use `Never` if this `Publisher` does not publish errors. public typealias Failure = Never /// This function is called to attach the specified `Subscriber` to this `Publisher` by `subscribe(_:)` public func receive<S>(subscriber: S) where Value == S.Input, S : Subscriber, S.Failure == Published<Value>.Publisher.Failure } /// The property that can be accessed with the `$` syntax and allows access to the `Publisher` public var projectedValue: Published<Value>.Publisher { mutating get } }
16. Default Publishers • Notification Center • URLSession • Just, Future • CurrentValueSubject, PassthroughSubject • NSManagedObject let ncpublisher = NotificationCenter.Publisher(center: .default, name: .NSCalendarDayChanged) let sessionPublisher = URLSession(configuration: .default) .dataTaskPublisher(for: URL(string: “https://api.google.com")!) let managedObject = NSManagedObject(context: context).publisher(for: \.hasChanges) let just = Just<String>("") let future = Future<String, Error> { (result) in result(.success("result")) result(.failure(TypedError.example)) }
17. From WWDC19 Introducing Combine One Many Synchronous Asynchronous Int Array Future Publisher
18. Subscriber
19. Publisher • Publisher͕ൃߦͨ͠஋΍Error, completionΛߪಡ͢Δ • ߪಡΛΩϟϯηϧͰ͖ΔʢCancellable)
20. public protocol Subscriber : CustomCombineIdentifierConvertible { /// The kind of values this subscriber receives. associatedtype Input /// The kind of errors this subscriber might receive. /// Use `Never` if this `Subscriber` cannot receive errors. associatedtype Failure : Error /// Tells the subscriber that it has successfully subscribed to the publisher and may request items. /// /// Use the received `Subscription` to request items from the publisher. func receive(subscription: Subscription) /// Tells the subscriber that the publisher has produced an element. func receive(_ input: Self.Input) -> Subscribers.Demand /// Tells the subscriber that the publisher has completed publishing, either normally or with an error. func receive(completion: Subscribers.Completion<Self.Failure>) } Subscriber
21. Assign
22. let labelTextSubscriber = Subscribers.Assign(object: label, keyPath: \.text) $queryPublisher .map { "searching for \($0)..." } .map(Optional.init) .subscribe(labelTextSubscriber) labelTextSubscriber.cancel() Assign
23. let cancellable = $queryPublisher .map { "searching for \($0)..." } .assign(to: \.text, on: label) // how to cancel cancellable.cancel() Assign
24. var cancellables = [AnyCancellable]() $queryPublisher .map { "searching for \($0)..." } .assign(to: \.text, on: label) .store(in: &cancellables) Assign
25. Sink
26. let labelTextSubscriber = Subscribers.Sink<String?, Never>(receiveCompletion: { _ in }) { self.label.text = $0 } $queryPublisher .map { "searching for \($0)..." } .subscribe(labelTextSubscriber) labelTextSubscriber.cancel() Sink
27. let cancellable = $queryPublisher .map { "searching for \($0)..." } .sink { self.label.text = $0 } cancellable.cancel() Sink
28. var cancellables = [AnyCancellable]() $queryPublisher .map { "searching for \($0)..." } .sink { self.label.text = $0 } .store(in: &cancellables) Sink
29. subscribe(on:) vs. receive(on:)
30. subscribe(on:) vs. receive(on:) • subscribe(on:) ͸ upstream messagesʹӨڹ • receive(on:) ͸downstream messagesͷ࣮ߦίϯςΩετʹӨڹ • ͜ͷྫͰ͸ɺpublisher΁ͷϦΫΤετ͸backgroundQueueͰߦΘΕΔ ͕ɺΤϨϝϯτΛड͚औΔͷ͸ϝΠϯεϨου let backgroundQueue = DispatchQueue(label: "background", qos: .utility) $queryPublisher .map { "searching for \($0)..." } .subscribe(on: backgroundQueue) .receive(on: DispatchQueue.main) .sink { self.label.text = $0 } .store(in: &cancellables)
31. The Pattern Subscriber is attached to Publisher Publisher sends a Subscription Subscriber requests N values Publisher sends N values or less Publisher sends completion Publisher Subscriber subscribe( ) receive(subscription:) request(_ : Demand) receive(completion:) receive(_ : Input) receive(_ : Input) • • •
32. Subject
33. Subject • PublisherͱSubscriberͷ྆ํͷੑ࣭Λ΋ͭ • ෳ਺ͷSubscriber΁஋ΛϒϩʔυΩϟετ͢Δ
34. Kinds of Subjects Passthrough CurrentValue
35. Kinds of Subjects Passthrough CurrentValue
36. Binding to SwiftUI
37. // Combine with SwiftUI class WizardModel : BindableObject { var trick: WizardTrick { didSet { didChange.send() } var wand: Wand? { didSet { didChange.send() } let didChange = PassthroughSubject<Void, Never>() } struct TrickView: View { @ObjectBinding var model: WizardModel var body: some View { Text(model.trick.name) } }
38. Operator
39. catch abortOnError allSatisfy append breakpoint breakpointOnError combineLatest compactMap count dropFirst filter first handleEvents ignoreOutput last log mapError max min output prefix prepend print removeDuplicates replaceEmpty replaceError replaceNil retry scan setFailureType switchToLatest zip map contains flatMap reduce merge drop collect From WWDC19 Introducing Combine
40. Error Handling
41. Failure Handling Operators assertNoFailure retry catch mapError setFailureType
42. https://github.com/freak4pc/rxswift-to-combine-cheatsheet/blob/master/Data/core_components.csv RxSwift to Combine
43. WWDC Sessions Introducing Combine WWDC19 Combine in Practice WWDC19 Data Flow through SwiftUI WWDC19
44. Great Presentations • https://speakerdeck.com/riteshhh/combine-all-the-things