async/awaitやactorでiOSアプリ開発がどう変わるか Before & Afterの具体例で学ぶ

今秋リリース予定のSwift 5.5には、async/awaitやactorなどの並行処理関連の新機能が多く含まれます。これによって、iOSアプリ開発における非同期処理や並行処理のコードは劇的に変化します。本トークでは、iOSアプリ開発でよく見かけるようなケースを取り上げ、Before & Afterのコードを示し、何がどのように変わるのかを説明します。

async/awaitやactorは使いこなせばとても便利ですが、新しい概念を初めから抽象的に学ぶのは大変です。しかし、それらが解決しようとしている問題自体はiOSアプリ開発者にとって馴染み深いものです。async/awaitやactorで書くコードが既存コードのどのような処理に対応するのか、既存コードにはどんな問題があり、async/awaitやactorはそれをどう解決してくれるのか、具体的なケースで学べば入口のハードルはぐっと下がります。

Swiftの並行処理関連の新機能は、async/await、async let、Task、CheckedContinuation、actor、Sendable、MainActorなど多岐に渡ります。それらを一つ一つ取り上げ、具体例を題材に、iOSアプリ開発のコードがどのように改善されるのかを説明します。

https://fortee.jp/iosdc-japan-2021/speaker/proposal/view/19c076c3-18cb-4d04-9e9d-59cc02220538

Transcript

1. async/await΍actorͰ iOSΞϓϦ։ൃ͕Ͳ͏มΘΔ͔ Before & A)erͷ۩ମྫͰֶͿ Yuta Koshizawa @koher
2. Swi$ 5.5
3. Concurrency ʢฒߦॲཧʣ
4. iOS ΞϓϦ։ൃΛܶతʹม͑Δ
5. Proposal: 12 ຊ WWDC: 9 ຊ
6. ۩ମతͳࣄྫ ↓ ந৅తͳ֓೦
7. iOS ΞϓϦ։ൃͱ͍͏۩ମྫ
8. Before & A)er ͷ۩ମྫͰֶͿ
9. 21 ݸͷέʔε
10. Concurrency ! async / await ! Structured Concurrency ! actor
11. ! async / await
12. Case 1: ඇಉظؔ਺ͷར༻ ΤϥʔϋϯυϦϯά͕ͳ͍৔߹
13. Before func downloadData(from url: URL, completion: @escaping (Data) -> Void)
14. Before func downloadData(from url: URL, completion: @escaping (Data) -> Void) downloadData(from: url) { data in // data Λ࢖͏ॲཧ }
15. async / await0296 0296 h'ps:/ /github.com/apple/swi9-evolu<on/blob/main/proposals/0296-async-await.md
16. Before func downloadData(from url: URL, completion: @escaping (Data) -> Void) downloadData(from: url) { data in // data Λ࢖͏ॲཧ }
17. A"er func downloadData(from url: URL) async -> Data let data = await downloadData(from: url) // data Λ࢖͏ॲཧ
18. A ͱ B ͕ಉ͡εϨουͰ࣮ߦ͞ΕΔͱ͸ݶΒͳ͍ func downloadData(from url: URL) async -> Data print("A") let data = await downloadData(from: url) print("B")
19. A ͱ B ͕ಉ͡εϨουͰ࣮ߦ͞ΕΔͱ͸ݶΒͳ͍ func downloadData(from url: URL, completion: @escaping (Data) -> Void) print("A") downloadData(from: url) { data in print("B") }
20. Case 3: ඇಉظؔ਺ͷར༻ ΤϥʔϋϯυϦϯά͕͋Δ৔߹
21. Case 1 (Before) func downloadData(from url: URL, completion: @escaping (Data) -> Void) downloadData(from: url) { data in // data Λ࢖͏ॲཧ }
22. Before func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) downloadData(from: url) { result in do { let data = try result.get() // data Λ࢖͏ॲཧ } catch { // ΤϥʔϋϯυϦϯά } }
23. A"er func downloadData(from url: URL) async throws -> Data do { let data = try await downloadData(from: url) // data Λ࢖͏ॲཧ } catch { // ΤϥʔϋϯυϦϯά }
24. Case 4: ඇಉظؔ਺ͷ࣮૷ ΤϥʔϋϯυϦϯά͕͋Δ৔߹
25. ྫ: User Λද͢ JSON Λऔಘͯ͠σίʔυ
26. Before func fetchUser(for id: User.ID, completion: @escaping (Result<User, Error>) -> Void) { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! }
27. Before func fetchUser(for id: User.ID, completion: @escaping (Result<User, Error>) -> Void) { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! downloadData(from: url) { result in } }
28. Before func fetchUser(for id: User.ID, completion: @escaping (Result<User, Error>) -> Void) { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! downloadData(from: url) { result in let data = try result.get() let user = try JSONDecoder().decode(User.self, from: data) completion(.success(user)) } }
29. Before func fetchUser(for id: User.ID, completion: @escaping (Result<User, Error>) -> Void) { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! downloadData(from: url) { result in do { let data = try result.get() let user = try JSONDecoder().decode(User.self, from: data) completion(.success(user)) } catch { completion(.failure(error)) } } }
30. Before func fetchUser(for id: User.ID, completion: @escaping (Result<User, Error>) -> Void) { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! downloadData(from: url) { result in do { let data = try result.get() let user = try JSONDecoder().decode(User.self, from: data) completion(.success(user)) } catch { completion(.failure(error)) } } }
31. A"er func fetchUser(for id: User.ID) async throws -> User { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! let data = try await downloadData(from: url) let user = try JSONDecoder().decode(User.self, from: data) return user }
32. Case 5: ඇಉظؔ਺ͷ࿈݁
33. ྫ: ϢʔβʔΞΠίϯͷμ΢ϯϩʔυ ʢͨͩ͠ɺΞΠίϯͷ URL ͸Ϣʔβʔͷ JSON ͷதʹهࡌʣ
34. Ϣʔβʔͷ JSON ͷμ΢ϯϩʔυ ↓ ΞΠίϯͷμ΢ϯϩʔυ
35. Before func fetchUserIcon(for id: User.ID, completion: @escaping (Result<Data, Error>) -> Void) { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! downloadData(from: url) { data in do { let data = try data.get() let user = try JSONDecoder().decode(User.self, from: data) downloadData(from: user.iconURL) { icon in do { let icon = try icon.get() completion(.success(icon)) } catch { completion(.failure(error)) } } } catch { completion(.failure(error)) } } }
36. A"er func fetchUserIcon(for id: User.ID) async throws -> Data { let url: URL = .init(string: "https://koherent.org/fake-service/api/user?id=\(id)")! let data = try await downloadData(from: url) let user = try JSONDecoder().decode(User.self, from: data) let icon = try await downloadData(from: user.iconURL) return icon }
37. Case 6: ίʔϧόοΫ͔Β async ΁ͷม׵
38. // ίʔϧόοΫ func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) // async func downloadData(from url: URL) async throws -> Data { }
39. // ίʔϧόοΫ func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) // async func downloadData(from url: URL) async throws -> Data { downloadData(from: url) { result in do { let data = try result.get() } catch { } } }
40. Con$nua$onSE-0300 SE-0300 h(ps:/ /github.com/apple/swi:-evolu<on/blob/main/proposals/0300-con<nua<on.md
41. // ίʔϧόοΫ func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) // async func downloadData(from url: URL) async throws -> Data { downloadData(from: url) { result in do { let data = try result.get() } catch { } } }
42. // ίʔϧόοΫ func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) // async func downloadData(from url: URL) async throws -> Data { try await withCheckedThrowingContinuation { continuation in downloadData(from: url) { result in do { let data = try result.get() continuation.resume(returning: data) } catch { continuation.resume(throwing: error) } } } }
43. // ίʔϧόοΫ func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) // async func downloadData(from url: URL) async throws -> Data { try await withCheckedThrowingContinuation { continuation in downloadData(from: url) { result in do { let data = try result.get() continuation.resume(returning: data) } catch { continuation.resume(throwing: error) } } } }
44. // ίʔϧόοΫ func downloadData(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) // async func downloadData(from url: URL) async throws -> Data { try await withCheckedThrowingContinuation { continuation in downloadData(from: url) { result in continuation.resume(with: result) } } }
45. ! Structured Concurrency
46. Case 7: ඇಉظॲཧͷ։࢝
47. async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺ΂ͳ͍ func foo() async { ... } func bar() async { await foo() // ✅ }
48. async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺ΂ͳ͍ func foo() async { ... } func bar() { await foo() // ⛔ }
49. async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺ΂ͳ͍ func foo() async { ... } func bar() async { await foo() } func baz() async { await bar() } ...
50. ඇಉظॲཧͷ։࢝ func main() { // ??? }
51. ඇಉظॲཧͷ։࢝ func main() { Task { await foo() } }
52. ඇಉظॲཧͷ։࢝ func main() { Task(operation: { await foo() }) }
53. ඇಉظॲཧͷ։࢝ func main() { Task { await foo() } } ͢΂ͯͷ async ؔ਺͸ Task ্Ͱ࣮ߦ͞ΕΔɻ
54. iOS ΞϓϦ։ൃͰͲͷΑ͏ʹ࢖ΘΕΔ͔ • viewDidAppear • View Controller ͕දࣔ͞ΕͨΒ fetchUser Ͱ User Λऔಘ ͯ͠දࣔ • @IBAction • μ΢ϯϩʔυϘλϯ͕ԡ͞ΕͨΒ downloadData Ͱμ΢ϯ ϩʔυ • ...
55. A"er extension UserViewController { override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) ɹ } }
56. A"er extension UserViewController { override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) do { let user = try await fetchUser(for: userID) self.user = user } catch { // ΤϥʔϋϯυϦϯά } } }
57. A"er extension UserViewController { override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) Task { do { let user = try await fetchUser(for: userID) self.user = user } catch { // ΤϥʔϋϯυϦϯά } } } }
58. Case 9: ฒߦॲཧ ݻఆݸ਺ͷ৔߹
59. ྫ: େখͷΞΠίϯΛಉ࣌ʹμ΢ϯϩʔυ
61. A"er func fetchUserIcons(for id: User.ID) async throws -> (small: Data, large: Data) { let smallURL: URL = ... let largeURL: URL = ... return icons }
62. ͜ΕͰ͸ฒߦʹͳΒͳ͍ func fetchUserIcons(for id: User.ID) async throws -> (small: Data, large: Data) { let smallURL: URL = ... let largeURL: URL = ... let smallIcon = try await downloadData(from: smallURL) let largeIcon = try await downloadData(from: largeURL) let icons = (small: smallIcon, large: largeIcon) return icons }
63. async let BindingSE-0317 SE-0317 h*ps:/ /github.com/apple/swi<-evolu>on/blob/main/proposals/0317-async-let.md
64. ͜ΕͰ͸ฒߦʹͳΒͳ͍ func fetchUserIcons(for id: User.ID) async throws -> (small: Data, large: Data) { let smallURL: URL = ... let largeURL: URL = ... let smallIcon = try await downloadData(from: smallURL) let largeIcon = try await downloadData(from: largeURL) let icons = (small: smallIcon, large: largeIcon) return icons }
65. A"er func fetchUserIcons(for id: User.ID) async throws -> (small: Data, large: Data) { let smallURL: URL = ... let largeURL: URL = ... async let smallIcon = downloadData(from: smallURL) async let largeIcon = downloadData(from: largeURL) let icons = try await (small: smallIcon, large: largeIcon) return icons }
66. A"er func fetchUserIcons(for id: User.ID) async throws -> (small: Data, large: Data) { let smallURL: URL = ... let largeURL: URL = ... async let smallIcon = downloadData(from: smallURL) async let largeIcon = downloadData(from: largeURL) let icons = try await (small: smallIcon, large: largeIcon) return icons } async let ͸ඞͣείʔϓ಺Ͱ await ͞Εͳ͚Ε͹ͳΒͳ͍ɻ
67. Structured ConcurrencySE-0304 SE-0304 h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0304-structured-concurrency.md
68. Structured Programming ʢߏ଄Խϓϩάϥϛϯάʣ
69. ߏ଄Խϓϩάϥϛϯά for value in values { if value.isValid { ... } else { ... } }
70. A"er func fetchUserIcons(for id: User.ID) async throws -> (small: Data, large: Data) { let smallURL: URL = ... let largeURL: URL = ... async let smallIcon = downloadData(from: smallURL) async let largeIcon = downloadData(from: largeURL) let icons = try await (small: smallIcon, large: largeIcon) return icons } async let ͸ඞͣείʔϓ಺Ͱ await ͞Εͳ͚Ε͹ͳΒͳ͍ɻ
71. async let ͱ Task Task { async let a = foo() async let b = bar() print(await a + b) }
74. Case 11: ඇಉظॲཧͷΩϟϯηϧ ඇಉظ API ͷར༻ଆ
75. Before func downloadData( from url: URL, cancellation: @escaping () -> Void, completion: @escaping (Result<Data, Error>) -> Void ) -> DownloadCanceller
76. Before extension ViewController { @IBAction func downloadButtonPressed(_ sender: UIButton) { ɹ ɹ ɹ } }
77. Before extension ViewController { @IBAction func downloadButtonPressed(_ sender: UIButton) { canceller = downloadData(from: url, cancellation: { // Ωϟϯηϧ࣌ͷॲཧ }, completion: { data in do { let data = try data.get() // data Λ࢖͏ॲཧ } catch { // ΤϥʔϋϯυϦϯά } }) } }
78. Before extension ViewController { @IBAction func cancelButtonPressed(_ sender: UIButton) { canceller?.cancel() canceller = nil } }
79. A"er func downloadData(from url: URL) async throws -> Data
80. A"er extension ViewController { @IBAction func downloadButtonPressed(_ sender: UIButton) { Task { } } }
81. A"er extension ViewController { @IBAction func downloadButtonPressed(_ sender: UIButton) { task = Task { } } }
82. A"er extension ViewController { @IBAction func cancelButtonPressed(_ sender: UIButton) { task?.cancel() task = nil } }
84. A"er extension ViewController { @IBAction func downloadButtonPressed(_ sender: UIButton) { task = Task { do { let data = try await downloadData(from: url) // data Λ࢖͏ॲཧ } catch { if Task.isCancelled { // Ωϟϯηϧ࣌ͷॲཧ } else { // ΤϥʔϋϯυϦϯά } } } } }
85. ! actor
86. Case 14: ڞ༗͞Εͨঢ়ଶͷมߋ
87. ڞ༗͞Εͨঢ়ଶΛಉ࣌ʹಡΈॻ͖ ↓ σʔλڝ߹
88. σʔλڝ߹ͷྫ final class Counter { private var count: Int = 0 func increment() -> Int { count += 1 return count } }
89. σʔλڝ߹ͷྫ let counter: Counter = .init() DispatchQueue.global().async { print(counter.increment()) // ? } DispatchQueue.global().async { print(counter.increment()) // ? }
90. σʔλڝ߹ͷྫ let counter: Counter = .init() DispatchQueue.global().async { print(counter.increment()) // 1 } DispatchQueue.global().async { print(counter.increment()) // 2 }
91. σʔλڝ߹ͷྫ let counter: Counter = .init() DispatchQueue.global().async { print(counter.increment()) // 2 } DispatchQueue.global().async { print(counter.increment()) // 1 }
92. σʔλڝ߹ͷྫ let counter: Counter = .init() DispatchQueue.global().async { print(counter.increment()) // 2 } DispatchQueue.global().async { print(counter.increment()) // 2 }
93. σʔλڝ߹ͷྫ final class Counter { private var count: Int = 0 func increment() -> Int { count += 1 return count } }
94. σʔλڝ߹Λ๷͙खஈ • ϩοΫ • γϦΞϧΩϡʔ
95. Before final class Counter { private let queue: DispatchQueue = .init(label: UUID().uuidString) private var count: Int = 0 func increment(completion: @escaping (Int) -> Void) { queue.async { [self] in count += 1 completion(count) } } }
96. Before let counter: Counter = .init() counter.increment { count in print(count) // 1 or 2 } counter.increment { count in print(count) // 2 or 1 }
97. actorSE-0306 Ͱղܾ SE-0306 h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0306-actors.md
98. A"er actor Counter { private var count: Int = 0 func increment() -> Int { count += 1 return count } }
99. σʔλڝ߹Λى͜͢ Counter final class Counter { private var count: Int = 0 func increment() -> Int { count += 1 return count } }
100. A"er actor Counter { private var count: Int = 0 func increment() -> Int { count += 1 return count } }
101. A"er actor Counter { private var count: Int = 0 func increment() async -> Int }
102. A"er let counter: Counter = .init() Task.detached { print(await counter.increment()) // 1 or 2 } Task.detached { print(await counter.increment()) // 2 or 1 }
103. Case 15: ڞ༗͞Εͨঢ়ଶͷมߋ Πϯελϯε಺Ͱͷϝιουݺͼग़͠
104. Counter ͷத͔Β Counter ͷϝιουΛ࢖͏ final class Counter { ... func increment(completion: @escaping (Int) -> Void) func incrementTwice(completion: @escaping (Int) -> Void) { } }
105. Counter ͷத͔Β Counter ͷϝιουΛ࢖͏ final class Counter { ... func increment(completion: @escaping (Int) -> Void) func incrementTwice(completion: @escaping (Int) -> Void) { increment { [self] _ in increment { count in completion(count) } } } }
106. ڝ߹ঢ়ଶͷྫ let counter: Counter = .init() counter.incrementTwice { count in print(count) // ? } counter.incrementTwice { count in print(count) // ? }
107. ڝ߹ঢ়ଶͷྫ let counter: Counter = .init() counter.incrementTwice { count in print(count) // 2 } counter.incrementTwice { count in print(count) // 4 }
108. ڝ߹ঢ়ଶͷྫ let counter: Counter = .init() counter.incrementTwice { count in print(count) // 3 } counter.incrementTwice { count in print(count) // 4 }
109. ڝ߹ঢ়ଶͷྫ final class Counter { ... func increment(completion: @escaping (Int) -> Void) func incrementTwice(completion: @escaping (Int) -> Void) { increment { [self] _ in increment { count in completion(count) } } } }
110. Before final class Counter { ... private func _increment() -> Int { count += 1 return count } func increment(completion: @escaping (Int) -> Void) { queue.async { [self] in _increment() completion(count) } } ... }
111. Before final class Counter { ... func incrementTwice(completion: @escaping (Int) -> Void) { queue.async { [self] in _increment() _increment() completion(count) } } }
112. A"er actor Counter { ... @discardableResult func increment() -> Int { count += 1 return count } func incrementTwice() -> Int { increment() increment() return count } }
113. Case 16: ڞ༗͞Εͨঢ়ଶͷมߋ ge#er
114. Case 14 (A*er) actor Counter { private var count: Int = 0 @discardableResult func increment() -> Int { count += 1 return count } }
115. A"er actor Counter { var count: Int = 0 @discardableResult func increment() -> Int { count += 1 return count } }
116. Effec%ul Read-only ϓϩύςΟSE-0310 class Foo { var value : Int { get { ... } } } SE-0310 h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0310-effecAul-readonly-proper=es.md
117. Effec%ul Read-only ϓϩύςΟSE-0310 class Foo { var value : Int { get async throws { ... } } } SE-0310 h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0310-effecAul-readonly-proper=es.md
118. A"er actor Counter { var count: Int { get async { ... } } ... }
119. A"er print(await counter.count)
120. Case 18: ڞ༗͞Εͨঢ়ଶͷมߋ ඇಉظॲཧ݁Ռͷ൓ө
121. ObservableObject ͷಋೖ final class UserViewController: UIViewController { private let state: UserViewState ... override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) state.loadUser() } }
122. ObservableObject ͷಋೖ final class UserViewController: UIViewController { ... override func viewDidLoad() { ... state .objectWillChange .receive(on: DispatchQueue.main) .sink { [self] _ in // state Λ View ʹ൓ө͢Δॲཧ } .store(in: &cancellables) } ... }
123. A"er actor UserViewState: ObservableObject { let userID: User.ID @Published var user: User? ... func loadUser() async { do { user = try await fetchUser(for: userID) } catch { // ΤϥʔϋϯυϦϯά } } }
124. A"er final class UserViewController: UIViewController { ... override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) state.loadUser() // } }
125. A"er final class UserViewController: UIViewController { ... override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) Task { await state.loadUser() // } } }
126. A"er state .objectWillChange .receive(on: DispatchQueue.main) .sink { [self] _ in // state Λ View ʹ൓ө͢Δॲཧ } .store(in: &cancellables)
127. A"er state .objectWillChange .receive(on: DispatchQueue.main) .sink { [self] _ in // state Λ View ʹ൓ө͢Δॲཧ let user = await state.user nameLabel.text = user?.name } .store(in: &cancellables)
128. A"er state .objectWillChange .receive(on: DispatchQueue.main) .sink { [self] _ in // state Λ View ʹ൓ө͢Δॲཧ Task { let user = await state.user nameLabel.text = user?.name } } .store(in: &cancellables)
129. Case 19: ΞΫλʔڥքΛӽ͑Δ
130. let user = await state.user
131. struct User { let id: ID var name: String var age: Int ... }
132. final class User { let id: ID var name: String var age: Int ... }
133. let user = await state.user // user?.age += 1 // actor ͷ֎͔Βมߋ
134. final class User { let id: ID let name: String let age: Int ... }
135. let user = await state.user // user?.age += 1 // ⛔
136. Sendable ϓϩτίϧSE-0302 SE-0302 h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0302-concurrent-value-and-concurrent- closures.md
137. struct User { let id: ID var name: String var age: Int ... }
138. struct User: Sendable { let id: ID var name: String var age: Int ... }
139. final class User: Sendable { let id: ID var name: String var age: Int ... } ⛔ var ϓϩύςΟΛ࣋ͭͷͰίϯύΠϧΤϥʔ
140. final class User: Sendable { let id: ID let name: String let age: Int ... } ✅ ΠϛϡʔλϒϧͳͷͰ OK
141. final class User: Sendable { let id: ID let name: NSString let age: Int ... } ⛔ Sendable Ͱͳ͍ܕͷϓϩύςΟΛ࣋ͭͷͰίϯύΠϧΤϥʔ
142. final class User: Sendable { let id: ID let firstName: String let familyName: String let age: Int var name: String { "\(firstName) \(familyName)" } ... } ✅ Computed Property Λ͍࣋ͬͯͯ΋ΠϛϡʔλϒϧͳͷͰ OK
143. final class User: Sendable { let id: ID let firstName: String let familyName: String let age: Int private var _name: String? // var name: String { if _name == nil { _name = "\(firstName) \(familyName)" } return _name! } ... }
144. final class User: @unchecked Sendable { let id: ID let firstName: String let familyName: String let age: Int private var _name: String? // var name: String { if _name == nil { _name = "\(firstName) \(familyName)" } return _name! } ... }
145. ϓϩτίϧʹద߹ͤ͞ΒΕͳ͍৔߹͸ʁ
146. actor Foo { func bar(_ f: (String) -> Int) { // // ... } }
147. actor Foo { func bar(_ f: @Sendable (String) -> Int) { // // ... } } Ϋϩʔδϟ͸ϓϩτίϧʹద߹Ͱ͖ͳ͍ͷͰ @Sendable Λ࢖͏
148. Case 20: ڞ༗͞Εͨঢ়ଶͷมߋ ϝΠϯεϨου্Ͱͷॲཧ
149. UserViewState ͷΩϡʔ͕ DispatchQueue.main ͩͱ͏Ε͍͠
150. UserViewState ͷΩϡʔ͕ DispatchQueue.main final class UserViewState: ObservableObject { private let queue: DispatchQueue = .main ... }
151. Case 18 (A*er) // queue ͸Πϯελϯε͝ͱʹࣗಈͰ࡞ΒΕΔ actor UserViewState: ObservableObject { ... }
152. Global ActorSE-0316 Ͱܕ΍ ΠϯελϯεΛӽ͑ͨ Actor Λ࡞Δ SE-0316 h*ps:/ /github.com/apple/swi<-evolu>on/blob/main/proposals/0316-global-actors.md
153. A"er @MainActorɹ final class UserViewState: ObservableObject { ... }
154. UIViewController h/ps:/ /developer.apple.com/documenta;on/uikit/uiviewcontroller
155. Case 18 (A*er) override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) Task { await state.loadUser() } }
156. A"er override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) state.loadUser() }
157. Case 18 (A*er) state .objectWillChange .receive(on: DispatchQueue.main) .sink { [self] _ in // state Λ View ʹ൓ө͢Δॲཧ Task { let user = await state.user nameLabel.text = user?.name } } .store(in: &cancellables)
158. A"er state .objectWillChange .receive(on: DispatchQueue.main) .sink { [self] _ in // state Λ View ʹ൓ө͢Δॲཧ nameLabel.text = state.user?.name } .store(in: &cancellables)
159. @MainActor ͸ @StateObject ʹ΋ඞਢ struct UserView: View { @StateObject private var state: UserViewState ... var body: some View { VStack { if let user = state.user { Text(user.name) } ... } .onAppear { state.loadUser() } } }
160. ʲ࿕ใʳSwi$ Concurrency ͸ iOS 13 Ҏ߱Ͱ ͋Ε͹ར༻Մೳʂ#39051 #39051 h)ps:/ /github.com/apple/swi;/pull/39051
161. ·ͱΊ • Concurrency ͰίʔυΛॻ͘ͷָ͕ʹͳΔ • ͔͠΋ɺΑΓ҆શʹʂ • ࠓ݄͔Β࢖͑Δʂʂʂ
162. h"ps:/ /zenn.dev/koher/ar1cles/swi6- concurrency-cheatsheet