Combine・sink（RxSwift・subscribe）では Task を作らないようにして async なメソッドを呼ぶ / Do not create a Task inside a Combine/sink (RxSwift/subscribe) closure when calling an async method there

Combine・sink（RxSwift・subscribe）では Task を作らないようにして async なメソッドを呼ぶ / Do not create a Task inside a Combine/sink (RxSwift/subscribe) closure when calling an async method there

公開 SwiftWednesday【iOSDC Japan 2023 直前】
2023/08/24 19:30〜
https://dena.connpass.com/event/291447/

登壇ノートはこちら: 準備中

Transcript

1. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. USFBTUSBJO
   
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 Task
   Λ࡞Βͳ͍Α͏ʹͯ͠
   
 async
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2. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ඇಉظॲཧͷҠߦ $PNCJOFɾ3Y4XJGU
   ˠ
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   FutureʢDeferred
   
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   SingleɾMaybeɾCompletable
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   Publisher
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   RxSwift.Observable 2
3. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ݺΜͰ͍ͨϝιου͕
   async
   ʹͳͬͨ 4XJGU
   $PODVSSFODZ
   ΁ͷҠߦ 3 import Combine import RxSwift import UIKit protocol PresenterProtocol { func handleEventA() func handleEventB() } final class ViewController: UIViewController { let presenter: some PresenterProtocol = ... // Combine let publisher: some Publisher<Output, Never> = ... var cancellables: [AnyCancellable] = [] // RxSwift let observable: RxSwift.Observable<Output> = ... let disposeBag = DisposeBag() override func viewDidLoad() { super.viewDidLoad() connect() } } extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in self?.presenter.handleEventA() } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in self?.presenter.handleEventB() } ) .disposed(by: disposeBag) } } async async
4. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ݺΜͰ͍ͨϝιου͕
   async
   ʹͳͬͨ 4XJGU
   $PODVSSFODZ
   ΁ͷҠߦ 4 import Combine import RxSwift import UIKit protocol PresenterProtocol { func handleEventA() async func handleEventB() async } final class ViewController: UIViewController { let presenter: some PresenterProtocol = ... // Combine let publisher: some Publisher<Output, Never> = ... var cancellables: [AnyCancellable] = [] // RxSwift let observable: RxSwift.Observable<Output> = ... let disposeBag = DisposeBag() override func viewDidLoad() { super.viewDidLoad() connect() } } extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in self?.presenter.handleEventA() } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in self?.presenter.handleEventB() } ) .disposed(by: disposeBag) } } 'async' call in a function that does not support concurrency
5. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ҟͳΔΞΫλʔͷϝιουΛݺͿ͜ͱʹͳͬͨ 4XJGU
   $PODVSSFODZ
   ΁ͷҠߦ 5 import Combine import RxSwift import UIKit protocol ViewProtocol: AnyObject { func handleEventA() func handleEventB() } final class ViewController: UIViewController { @ViewLoading var object: ViewObject<ViewController> override func viewDidLoad() { super.viewDidLoad() object = .init(view: self) } } extension ViewController: ViewProtocol { ... } final class ViewObject<View: ViewProtocol> { unowned let view: View ... func connect() { publisher .sink( receiveValue: { [weak self] output in self?.view.handleEventA() } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in self?.view.handleEventB() } ) .disposed(by: disposeBag) } } @MainActor
6. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ҟͳΔΞΫλʔͷϝιουΛݺͿ͜ͱʹͳͬͨ 4XJGU
   $PODVSSFODZ
   ΁ͷҠߦ 6 import Combine import RxSwift import UIKit @MainActor protocol ViewProtocol: AnyObject { func handleEventA() func handleEventB() } final class ViewController: UIViewController { @ViewLoading var object: ViewObject<ViewController> override func viewDidLoad() { super.viewDidLoad() object = .init(view: self) } } extension ViewController: ViewProtocol { ... } final class ViewObject<View: ViewProtocol> { unowned let view: View ... func connect() { publisher .sink( receiveValue: { [weak self] output in self?.view.handleEventA() } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in self?.view.handleEventB() } ) .disposed(by: disposeBag) } } Call to main actor-isolated instance method * in a synchronous nonisolated context
7. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. 4XJGU
   $PODVSSFODZ
   ΁ͷҠߦ ίϯύΠϧ࣌ͷΤϥʔΛղফ͢Δʹ͸ w Πϕϯτड৴࣌ʹ
   async
   ͳ 
 ϝιουΛ࣮ߦͨ͘͠ͳͬͨ
   㾎Task
   Λ࡞ͬͯݺͿ
   w Πϕϯτड৴࣌ʹ 
 ҟͳΔΞΫλʔʹ෼཭͞Ε͍ͯΔ 
 ϝιουΛ࣮ߦͨ͘͠ͳͬͨ
   㾎Task
   Λ࡞ͬͯݺͿ
   㾎ಉ͡ΞΫλʔͰ࣮ߦ͢ΔΑ͏ʹ ݺͿ 7
8. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Πϕϯτड৴৔ॴͰ
   Task
   Λ࡞ͬͯ
   await async
   ͳϝιουΛݺͿͱ͖ 8 extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in self?.presenter.handleEventA() } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in self?.presenter.handleEventB() } ) .disposed(by: disposeBag) } } extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in Task { await self?.presenter.handleEventA() } } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in Task { await self?.presenter.handleEventB() } } ) .disposed(by: disposeBag) } }
9. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Πϕϯτड৴৔ॴͰ
   Task
   Λ࡞ͬͯ
   await async
   ͳϝιουΛݺͿͱ͖ w self
   ͸͜ͷ··Ͱ͍͍ͷ͔ʜʜʁ
   w ࣮ߦ͞Εͨ
   Task
   ͷΩϟϯηϧΛ Ͳ͏͠Α͏ʜʜ
   w $PNCJOFɾ3Y4XJGU
   ͷ 
 4DIFEVMFS
   ͷࢦఆ͸ʜʜʁ
   w ωετ͕ਂ͍ʜʜ 9 extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in Task { await self?.presenter.handleEventA() } } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in Task { await self?.presenter.handleEventB() } } ) .disposed(by: disposeBag) } }
10. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ΠϕϯτΛ 
 AsyncSequence
    Ͱड৴͢Δ 10
11. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. AsyncSequence ͓͞Β͍ w Sequence
    ͷඇಉظ൛
    w for-in
    ϧʔϓΛॻ͚Δ 11 let numbers: some Sequence = [0, 1, 2, 3] for number in numbers { print(number, terminator: " ") } // "0 1 2 3 " var iterator = [0, 1, 2, 3].makeIterator() let counter: some AsyncSequence = AsyncStream { try? await Task.sleep(for: .seconds(1)) return iterator.next() } for try await count in counter { print(count, terminator: " ") } // "0 1 2 3 "
12. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. AsyncSequence ͓͞Β͍ w Sequence
    ͷඇಉظ൛
    w for-in
    ϧʔϓΛॻ͚Δ
    w for-await-in
    ϧʔϓΛॻ͚Δ
    w ࣦഊ͢ΔՄೳੑ͕͋ΔͳΒ 
 for-try-await-in
    ϧʔϓ 12 let numbers: some Sequence = [0, 1, 2, 3] for number in numbers { print(number, terminator: " ") } // "0 1 2 3 " var iterator = [0, 1, 2, 3].makeIterator() let counter: some AsyncSequence = AsyncStream { try? await Task.sleep(for: .seconds(1)) return iterator.next() } for try await count in counter { print(count, terminator: " ") } // "0 1 2 3 "
13. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ༻ҙ͞Ε͍ͯΔΠϯελϯεϓϩύςΟ ͍ͣΕ΋
    AsyncSequence
    ʹద߹͍ͯ͠Δ w $PNCJOF
    w 3Y4XJGUʢ3Y4XJGU
     ʣ 13 extension Publisher where Self.Failure == Never { @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *) public var values: AsyncPublisher<Self> { get } } extension Publisher { @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *) public var values: AsyncThrowingPublisher<Self> { get } } #if swift(>=5.5.2) && canImport(_Concurrency) import Foundation @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) public extension ObservableConvertibleType { var values: AsyncThrowingStream<Element, Error> { get } } #endif #if swift(>=5.5.2) && canImport(_Concurrency) && !os(Linux) @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) public extension InfallibleType { var values: AsyncStream<Element> { get } } #endif
14. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. values
    Λ࢖ͬͯ
    for-await-in
    ϧʔϓͰड৴
    await
    ͕࢖͑ͯ
    ίʔυ͕୹͘ͳΓ
    ωετ΋ઙ͘ͳͬͨ 14 extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in Task { await self?.presenter.handleEventA() } } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in Task { await self?.presenter.handleEventB() } } ) .disposed(by: disposeBag) } } extension ViewController { func connect() { Task { for await output in publisher.values { await presenter.handleEventA() } } Task { for try await output in observable.values { await presenter.handleEventB() } } } }
15. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. values
    Λ࢖ͬͯ
    for-await-in
    ϧʔϓͰड৴
    await
    ͕࢖͑ͯ
    ίʔυ͕୹͘ͳΓ
    ωετ΋ઙ͘ͳͬͨ 15 extension ViewController { func connect() { publisher .sink( receiveValue: { [weak self] output in Task { await self?.presenter.handleEventA() } } ) .store(in: &cancellables) observable .subscribe( onNext: { [weak self] output in Task { await self?.presenter.handleEventB() } } ) .disposed(by: disposeBag) } } extension ViewController { func connect() { Task { for await output in publisher.values { await presenter.handleEventA() } } Task { for try await output in observable.values { await presenter.handleEventB() } } } } 🎉
16. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ࣮ࡍʹಈ͔ͯ͠ΈΔ for-await-in
    ϧʔϓͰड৴
    16 import Combine import UIKit final class ViewController: UIViewController { deinit { print(self, "is deinited 🎉") } override func viewDidLoad() { // ... connect() } let publisher: some Publisher<Output, Never> = ... func connect() { Task { for await output in publisher.values { // ... } } } } EFJOJU
    ͕ݺ͹Εͳ͍ʜʜ GPSBXBJUJO
    ϧʔϓΛ 
 ऴྃͤ͞Δज़͕ͳ͍
17. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. handleEventsɾreceiveCancel
    ͕ݺ͹Εͳ͍ 3Y4XJGU
    ͳΒ
    doɾonDispose 17 import Combine import UIKit final class ViewController: UIViewController { // ... func connect() { Task { let values = publisher .handleEvents( receiveCancel: { print("receiveCancel") } ) .values for await output in values { // ... } } } // ... } ݺ͹Εͳ͍ʜʜ Ωϟϯηϧ͞Εͣʹ଴͍ͬͯΔ
18. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. handleEventsɾreceiveCancel
    ͕ݺ͹Εͳ͍ 3Y4XJGU
    ͳΒ
    doɾonDispose 18 import Combine import UIKit final class ViewController: UIViewController { // ... func connect() { Task { let values = publisher .handleEvents( receiveCancel: { print("receiveCancel") } ) .values for await output in values { // ... } } } // ... } import Combine import UIKit final class ViewController: UIViewController { // ... private var cancellables: [AnyCancellable] = [] func connect() { publisher .handleEvents( receiveCancel: { print("receiveCancel") } ) .sink( receiveValue: { [weak self] output in // ... } ) .store(in: &cancellables) } // ... } ݺ͹Εͳ͍ʜʜ Ωϟϯηϧ͞Εͣʹ଴͍ͬͯΔ ݺ͹ΕΔʂ
19. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. for-await-in
    ͷ͋Δ
    Task
    ʹ 
 ΩϟϯηϧΛ఻͑Δ 19
20. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. for-await-in
    ͷ͋Δ
    Task
    ʹΩϟϯηϧΛ఻͑Δ ͞·͟·ͳํ๏͕͋Δ w Task
    Λ
    $PNCJOF
    ͷ
    Cancellable
    ʹద߹ͤ͞ɺ $PNCJOF
    ͷ
    Publisher
    ͱ 
 ಉ͡Α͏ʹ 
 store(in: &cancellables)
    w ΦϦδφϧͰ
    CancelBag
    Λ࡞Δ 
 ʢDisposeBag
    ͷΑ͏ͳʣ
    w Task
    Λอ͓͖࣋ͯ͠ɺ 
 deinit
    ͳͲͷλΠϛϯάͰ
    Task.cancel()
    ΛࣗΒݺͿ
    w ෳ਺͋Δ৔߹͸
    TaskGroup
    Ͱ ·ͱΊͯ΋Α͍ 
 
 
 ɹɹɹɹɹɹɹɹɹ
    FUD 20
21. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. Task
    Λ
    $PNCJOF
    ͷ
    Cancellable
    ʹ͢Δ ݁ہ
    $PNCJOF
    ͕ཁΔ͕
    ͓खܰ 21 extension ViewController { func connect() { Task { for await output in publisher.values { await presenter.handleEventA() } } Task { for try await output in observable.values { await presenter.handleEventB() } } } } import Combine import Foundation extension Task: Cancellable {} import Combine import UIKit final class ViewController: UIViewController { private let publisher: some Publisher<Output, Never> = ... private var cancellables: [AnyCancellable] = [] // ... func connect() { Task { [publisher] in for await output in publisher.values { // ... } } .store(in: &cancellables) } // … }
22. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. deinit
    ͳͲͷλΠϛϯάͰ
    Task.cancel()
    ΛݺͿ deinit
    ͕ݺ͹ΕΔΑ͏ʹ஫ҙ͢Δʢself
    ΛΩϟϓνϟ͠ͳ͍ʣ 22 extension ViewController { func connect() { Task { for await output in publisher.values { await presenter.handleEventA() } } Task { for try await output in observable.values { await presenter.handleEventB() } } } } final class ViewController: UIViewController { var task1: Task<(), Never>? var task2: Task<(), any Error>? deinit { task1?.cancel() task2?.cancel() } ... } extension ViewController { func connect() { task1 = Task { [publisher, presenter] in for await output in publisher.values { await presenter.handleEventA() } } task2 = Task { [publisher, presenter] in ... } } }
23. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ·ͱΊ $PNCJOFɾ3Y4XJGU
    ˠ
    4XJGU
    $PODVSSFODZ w $PNCJOFɾ3Y4XJGU
    ͷΠϕϯτΛ 
 4XJGU
    $PODVSSFODZʢAsyncSequenceʣͰ 
 ड͚औΕΔ࢓૊Έ͕༻ҙ͞Ε͍ͯΔ
    w Ҡߦظʹศརʹ࢖͑ͦ͏
    w ΩϟϯηϧΛࣗ෼ͰߦΘͳ͍ͱղ์͞Εͣʹ࢒ͬͯ͠·͏ͷͰ஫ҙ͢Δ 23
24. Copyright © 2023 treastrain / Tanaka RyogaɹAll rights reserved. ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ $PNCJOFɾsinkʢ3Y4XJGUɾsubscribeʣͰ͸ 
 Task
    Λ࡞Βͳ͍Α͏ʹͯ͠
    
 async
    ͳϝιουΛݺͿ 4XJGU8FEOFTEBZ 24 ެ։
    4XJGU8FEOFTEBZʲJ04%$
    +BQBO
    
    ௚લʳ
    
    "VHVTU