Swift Zoomin' #8

Transcript

1. Swi$ Zoomin' #8
   Actor ϋϯζΦϯ
   

   View Slide

2. Actor ͱ͸
   

   View Slide

3. ɾɾɾͷલʹ
   

   View Slide

4. Actor ͸ async/await Λଟ༻͢Δ
   

   View Slide

5. async/await ͷ؆୯ͳ෮श
   

   View Slide

6. ίʔϧόοΫʹΑΔඇಉظؔ਺
   // એݴ
   func downloadData(from url: URL,
   completion: @escaping (Data) -> Void)
   // ར༻
   downloadData(from: url) { data in
   // data Λ࢖͏ॲཧ
   }
   

   View Slide

7. async/await ʹΑΔඇಉظؔ਺
   // એݴ
   func downloadData(from url: URL) async -> Data
   // ར༻
   let data = await downloadData(from: url)
   // data Λ࢖͏ॲཧ
   

   View Slide

8. ίʔϧόοΫʹΑΔඇಉظؔ਺
   // એݴ
   func downloadData(from url: URL,
   completion: @escaping (Result) -> Void)
   // ར༻
   downloadData(from: url) { result in
   do {
   let data = try result.get()
   // data Λ࢖͏ॲཧ
   } catch { /* ΤϥʔϋϯυϦϯά */ }
   }
   

   View Slide

9. async/await ʹΑΔඇಉظؔ਺
   // એݴ
   func downloadData(from url: URL) async throws -> Data
   // ར༻
   do {
   let data = try await downloadData(from: url)
   // data Λ࢖͏ॲཧ
   } catch { /* ΤϥʔϋϯυϦϯά */ }
   

   View Slide

10. ࿅श໰୊༻ϦϙδτϦ
    h"ps:/
    /github.com/koher/swi4-zoomin-8
    

    View Slide

11. Q1: downloadData
    ίʔϧόοΫͰ݁ՌΛฦ͢ downloadData ؔ਺͕
    Download.swi, ʹ࣮૷͞Ε͍ͯ·͢ɻ async/await Λར༻͠
    ͯɺ໭Γ஋Ͱ݁ՌΛฦ͢ downloadData ؔ਺Λ࣮૷ͯ͠Լ͞
    ͍ɻ
    !
    iOS 15 ͔Β URLSession ʹ௥Ճ͞Εͨ࣍ͷϝιου͕໾ʹཱ
    ͪ·͢ɻ1
    func data(from url: URL) async throws -> (Data, URLResponse)
    1 h$ps:/
    /developer.apple.com/documenta6on/founda6on/urlsession/3767353-data
    

    View Slide

12. Q1: ղ౴ྫ
    

    View Slide

13. async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺͼग़ͤͳ͍
    func foo() async
    func bar() async {
    await foo() //
    ✅
    OK
    }
    

    View Slide

14. async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺͼग़ͤͳ͍
    func foo() async
    func bar() {
    await foo() //
    ⛔
    NG
    }
    

    View Slide

15. async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺͼग़ͤͳ͍
    func foo() async
    func bar() async {
    await foo() //
    ✅
    OK
    }
    func baz() async {
    await bar() //
    ✅
    OK
    }
    ...
    

    View Slide

16. async ؔ਺Λ࠷ॳʹݺͼग़͢ͱ͖͸ʁ
    

    View Slide

17. ಉظؔ਺͔Βͷ async ؔ਺ͷݺͼग़͠
    override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    await foo() //
    ⛔
    NG
    }
    

    View Slide

18. ಉظؔ਺͔Βͷ async ؔ਺ͷݺͼग़͠
    override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    Task {
    await foo() //
    ✅
    OK
    }
    }
    

    View Slide

19. ಉظؔ਺͔Βͷ async ؔ਺ͷݺͼग़͠
    override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    Task(operation: {
    await foo() //
    ✅
    OK
    })
    }
    

    View Slide

20. Task.init 2
    @discardableResult
    init(
    priority: TaskPriority? = nil,
    operation: @escaping @Sendable () async throws -> Success
    )
    2 h$ps:/
    /developer.apple.com/documenta6on/swi9/task/3856790-init
    

    View Slide

21. Q2: UserViewController.viewDidAppear
    UserViewController ͸ User ͷ৘ใΛऔಘͯ͠දࣔ͢Δ View
    Controller Ͱ͢ɻ viewDidAppear ͷதͰ downloadData ؔ਺Λ
    ࢖͍ɺ User ͱΞΠίϯΛऔಘͯ͠දࣔ͠·͢ɻ
    ͜ΕΛɺ async/await Ͱ࣮૷͞Εͨ downloadData ؔ਺Λར
    ༻ͯ͠࠶࣮૷ͯ͠Լ͍͞ɻ
    

    View Slide

22. Q2: ղ౴ྫ
    

    View Slide

23. Actor ͱ͸
    

    View Slide

24. Actor ͸ΫϥεʹࣅͨࢀরܕͰɺσʔλڝ߹
    Λ๷͙ͨΊͷϘΠϥʔϓϨʔτ͕ෆཁʹͳ
    Δɻ
    ͦͷͨΊɺίʔυ͕؆͔ܿͭ҆શʹͳΔɻ
    

    View Slide

25. σʔλڝ߹ͱ͸
    

    View Slide

26. Χ΢ϯλʔͷσʔλڝ߹
    final class Counter {
    private var count: Int = 0
    func increment() -> Int {
    count += 1
    return count
    }
    }
    

    View Slide

27. Χ΢ϯλʔͷσʔλڝ߹
    let counter: Counter = .init()
    Task {
    print(counter.increment()) // ?
    }
    Task {
    print(counter.increment()) // ?
    }
    

    View Slide

28. Χ΢ϯλʔͷσʔλڝ߹
    let counter: Counter = .init()
    Task {
    print(counter.increment()) // 1
    }
    Task {
    print(counter.increment()) // 2
    }
    

    View Slide

29. Χ΢ϯλʔͷσʔλڝ߹
    let counter: Counter = .init()
    Task {
    print(counter.increment()) // 2
    }
    Task {
    print(counter.increment()) // 1
    }
    

    View Slide

30. Χ΢ϯλʔͷσʔλڝ߹
    let counter: Counter = .init()
    Task {
    print(counter.increment()) // 2
    }
    Task {
    print(counter.increment()) // 2
    }
    

    View Slide

31. Χ΢ϯλʔͷσʔλڝ߹
    final class Counter {
    private var count: Int = 0
    func increment() -> Int {
    count += 1
    Thread.sleep(forTimeInterval: 1.0)
    return count
    }
    }
    

    View Slide

32. Χ΢ϯλʔͷσʔλڝ߹
    let counter: Counter = .init()
    Task {
    print(counter.increment()) // 1
    }
    Task {
    print(counter.increment()) // 1
    }
    

    View Slide

33. final class Counter {
    private var count: Int = 0
    func increment() -> Int {
    let count = self.count
    Thread.sleep(forTimeInterval: 1.0)
    self.count = count + 1
    return self.count
    }
    }
    

    View Slide

34. σʔλڝ߹΁ͷରԠํ๏
    • ϩοΫ
    • ʢ DispatchQueue ͷʣγϦΞϧΩϡʔ
    

    View Slide

35. γϦΞϧΩϡʔʹΑΔσʔλڝ߹ͷղফ
    final class Counter {
    private let queue: DispatchQueue
    = .init(label: "Counter")
    private var count: Int = 0
    func increment(completion: @escaping (Int) -> Void) {
    queue.async { [self] in
    count += 1
    completion(count)
    }
    }
    }
    

    View Slide

36. γϦΞϧΩϡʔʹΑΔσʔλڝ߹ͷղফ
    let counter: Counter = .init()
    Task {
    counter.increment { print($0) } // 1
    }
    Task {
    counter.increment { print($0) } // 2
    }
    

    View Slide

37. γϦΞϧΩϡʔʹΑΔσʔλڝ߹ͷղফ
    final class Counter {
    private let queue: DispatchQueue
    = .init(label: "Counter")
    private var count: Int = 0
    func increment(completion: @escaping (Int) -> Void) {
    queue.async { [self] in
    count += 1
    completion(count)
    }
    }
    }
    

    View Slide

38. σʔλڝ߹΁ͷରԠํ๏
    • ϩοΫ
    • ʢ DispatchQueue ͷʣγϦΞϧΩϡʔ
    • Actor
    

    View Slide

39. Actor ʹΑΔσʔλڝ߹ͷղফ
    final class Counter {
    private var count: Int = 0
    func increment() -> Int {
    count += 1
    return count
    }
    }
    

    View Slide

40. Actor ʹΑΔσʔλڝ߹ͷղফ
    actor Counter {
    private var count: Int = 0
    func increment() -> Int {
    count += 1
    return count
    }
    }
    

    View Slide

41. Actor ʹΑΔσʔλڝ߹ͷղফ
    let counter: Counter = .init()
    Task {
    print(await counter.increment())
    }
    Task {
    print(await counter.increment())
    }
    

    View Slide

42. Q3: BankAccount.deposit
    ࣍ͷΑ͏ͳ BankAccount ΫϥεΛ࣮૷͠ɺฒߦʹ༬ۚ͢Δ͜ͱ
    Ͱσʔλڝ߹͕ൃੜ͢Δ͜ͱΛ֬ೝͯ͠Լ͍͞ɻͦͷޙɺ
    BankAccount Λ actor ʹมߋ͠ɺσʔλڝ߹͕๷ࢭ͞ΕΔ͜ͱ
    Λ֬ೝͯ͠Լ͍͞ɻ
    final class BankAccount { // ۜߦޱ࠲
    var balance: Int = 0 // ༬ۚ࢒ߴ
    func deposit(_ amount: Int) -> Int // ೖۚʢ໭Γ஋͸࢒ߴʣ
    }
    

    View Slide

43. Q3: ղ౴ྫ
    

    View Slide

44. Actor ͷಉҰΠϯελϯε಺Ͱͷϝιουݺͼग़͠
    actor A {
    func foo() { ... }
    func bar() {
    foo() // ಉظ
    }
    }
    await foo() // ඇಉظ
    

    View Slide

45. Q4: BankAccount.getInterest
    BankAccount ʹ getInterest ϝιουΛ࣮૷ͯ͠Լ͍͞ɻ
    getInterest ϝιου͸࣍ͷΑ͏ͳγάωνϟΛ࣋ͪɺҾ਺Ͱ
    ར཰Λड͚औΓɺͦΕΛݩʹརଉΛܭࢉͯ͠༬ۚ࢒ߴΛมಈͤ͞
    ্ͨͰɺ৽͍͠༬ۚ࢒ߴΛฦ͢΋ͷͱ͠·͢ɻͨͩ͠ɺ༬ۚ࢒ߴ
    ͷมಈʹ͸ deposit ϝιουΛར༻͢Δ΋ͷͱ͠·͢ɻ
    func getInterest(with rate: Double) -> Int
    

    View Slide

46. Q4: ղ౴ྫ
    

    View Slide

47. Actor ͷΠϯελϯεؒͰͷϝιουݺͼग़͠
    actor A {
    func foo() { ... }
    }
    actor B {
    func bar(a: A) async {
    await a.foo() // ඇಉظ
    }
    }
    

    View Slide

48. Actor ͷΠϯελϯεؒͰͷϝιουݺͼग़͠
    actor A {
    func foo() { ... }
    func bar(a: A) async {
    foo() // ಉظ
    await a.foo() // ඇಉظ
    }
    }
    

    View Slide

49. Actor ͷΠϯελϯεؒͰͷϝιουݺͼग़͠
    actor A {
    func foo() { ... }
    func bar(a: A) async {
    self.foo() // ಉظ
    await a.foo() // ඇಉظ
    }
    }
    

    View Slide

50. Actor ͷΠϯελϯεؒͰͷϝιουݺͼग़͠
    actor A {
    func foo() { ... }
    func bar(a: A) async {
    foo() // ಉظ
    await a.foo() // ඇಉظ
    }
    }
    

    View Slide

51. Q5: BankAccount.transfer
    BankAccount ʹ࣍ͷೋͭͷϝιουΛ௥Ճͯ͠Լ͍͞ɻ
    • ޱ࠲͔Βग़ۚ͢ΔͨΊͷ withdraw ϝιου
    • ޱ࠲ؒͰૹۚ͢ΔͨΊͷ transfer ϝιου
    // ࢒ߴ͕଍Γͳ͍৔߹͸ΤϥʔΛ throw
    func withdraw(_ amount: Int) throws -> Int // ໭Γ஋͸࢒ߴ
    func transfer(_ amount: Int, to account: BankAccount) async throws
    

    View Slide

52. Q5: ղ౴ྫ
    

    View Slide

53. Sendable
    

    View Slide

54. Sendable 3
    actor ڥքΛ௒͑ͯ΍ΓͱΓͰ͖Δ͜ͱΛද͢ϓϩτίϧ
    3 h$ps:/
    /github.com/apple/swi6-evolu9on/blob/main/proposals/0302-concurrent-value-and-concurrent-
    closures.md
    

    View Slide

55. final class User {
    let id: ID
    var name: String
    var age: Int
    ...
    }
    

    View Slide

56. actor A {
    let user: User = ...
    }
    let a: A = ...
    Task {
    let user = await a.user
    user.age += 1 //
    ⛔
    }
    Actor ͷΩϡʔͷ֎Ͱ Actor ͷ಺෦ঢ়ଶΛมߋͰ͖ͯ͠·͏
    

    View Slide

57. final class User: Sendable {
    let id: ID
    var name: String
    var age: Int
    ...
    }
    ⛔
    ࢀরܕͰ var ϓϩύςΟΛ࣋ͭͷͰίϯύΠϧΤϥʔ
    

    View Slide

58. struct User {
    let id: ID
    var name: String
    var age: Int
    ...
    }
    public Ͱͳ͍஋ܕ͸҉໧తʹద߹4
    4 h$ps:/
    /github.com/apple/swi6-evolu9on/blob/main/proposals/0302-concurrent-value-and-concurrent-
    closures.md#implicit-structenum-conformance-to-sendable
    

    View Slide

59. public struct User: Sendable {
    public let id: ID
    public var name: String
    public var age: Int
    ...
    }
    public ͩͱ໌ࣔతʹద߹ͤ͞Δඞཁ͋Γ
    

    View Slide

60. struct User: Sendable {
    let id: ID
    var name: NSString
    var age: Int
    ...
    }
    ⛔
    Sendable Ͱͳ͍ϝϯόʔΛ࣋ͭͷͰίϯύΠϧΤϥʔ
    

    View Slide

61. final class User: Sendable {
    let id: ID
    let name: String
    let age: Int
    ...
    }
    ✅
    ࢀরܕͰ΋ΠϛϡʔλϒϧͳΒ OK
    

    View Slide

62. 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
    

    View Slide

63. 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!
    }
    ...
    }
    

    View Slide

64. 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!
    }
    ...
    }
    

    View Slide

65. actor Counter {
    private var count: Int = 0
    func increment() -> Int {
    count += 1
    return count
    }
    }
    actor ͸҉໧తʹ Sendable ʹద߹
    

    View Slide

66. ϓϩτίϧʹద߹ͤ͞ΒΕͳ͍৔߹͸ʁ
    

    View Slide

67. actor Foo {
    func bar(_ f: (String) -> Int) { //
    // ...
    }
    }
    

    View Slide

68. actor Foo {
    func bar(_ f: @Sendable (String) -> Int) { //
    // ...
    }
    }
    Ϋϩʔδϟ͸ϓϩτίϧʹద߹Ͱ͖ͳ͍ͷͰ @Sendable Λ࢖͏
    

    View Slide

69. final class User {
    var name: String
    ...
    }
    let user: User = ...
    Task {
    let name = user.name //
    }
    @Sendable Ϋϩʔδϟ͸ Sendable ͳ஋͔͠ΩϟϓνϟͰ͖ͳ
    ͍ʢ Task.init ʹ౉͢Ϋϩʔδϟ͸ @Sendable ʣ
    

    View Slide

70. var a = 42
    Task {
    print(a) //
    ⛔
    }
    @Sendable Ϋϩʔδϟ͸ม਺ΛΩϟϓνϟͰ͖ͳ͍
    

    View Slide

71. var a = 42
    Task { [a] in
    print(a) //
    ✅
    }
    by-value Ωϟϓνϟ͸Մೳ
    

    View Slide

72. View Slide

73. Actor-isolated Context ͷҾܧ͗
    

    View Slide

74. @nonescaping, non-@Sendable
    ʢ context ΛҾ͖ܧ͙ʣ
    actor A {
    func foo(values: [Int]) {
    // A
    values.forEach { value in
    // A
    }
    }
    }
    

    View Slide

75. @escaping, non-@Sendableʢ context ΛҾ͖ܧ͙ʣ
    actor A {
    func foo(value: Int) {
    // A
    let square: (Int) -> Int = { // @escaping
    // A
    $0 * $0
    }
    print(square(value))
    print(square(square(value)))
    }
    }
    

    View Slide

76. @Sendable ʢ context ΛҾ͖ܧ͕ͳ͍ʣ
    actor A {
    func foo() {
    // A
    let foo: Foo = .init() // Foo: Sendable
    DispatchQueue.global().async { [foo] in // @Sendable
    // not A
    foo.value = 2
    }
    foo.value = 3
    print(foo.value)
    }
    }
    ※ͨͩ͠ɺ Swi% 5.5 ݱࡏ͸ @Sendable Ͱͳ͍
    

    View Slide

77. Task.initʢ context ΛҾ͖ܧ͙ʣ
    actor A {
    func foo() {
    // A
    Task { // @Sendable
    // A
    }
    }
    }
    

    View Slide

78. @_inheritActorContext
    extension Task where Failure == Never {
    ...
    @discardableResult
    @_alwaysEmitIntoClient
    public init(
    priority: TaskPriority? = nil,
    @_inheritActorContext @_implicitSelfCapture
    operation: __owned @Sendable @escaping () async -> Success
    ) {
    ...
    }
    }
    10 h%ps:/
    /github.com/apple/swi7/blob/main/stdlib/public/Concurrency/Task.swi7
    

    View Slide

79. Task.initʢ context ΛҾ͖ܧ͙ʣ
    actor A {
    func foo() {
    // A
    Task { // @Sendable
    // A
    }
    }
    }
    

    View Slide

80. Task.detachedʢ context ΛҾ͖ܧ͕ͳ͍ʣ
    actor A {
    func foo() {
    // A
    Task.detached { // @Sendable
    // not A
    }
    }
    }
    

    View Slide

81. Actor-isolated Context ͷҾܧ͗ͷؔ͢Δ
    swi2-developers-japan Ͱͷ΍ΓͱΓ11
    11 h$ps:/
    /discord.com/channels/291054398077927425/291054454793306112/890858321693769748
    

    View Slide

82. UserViewController
    

    View Slide

83. View Slide

84. override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    Task {
    do {
    // User ͷ JSON ͷऔಘ
    let url: URL = ...
    let data = try await downloadData(from: url)
    ...
    // View ΁ͷ൓ө
    iconImageView.image = iconImage
    } catch {
    // ΤϥʔϋϯυϦϯά
    print(error)
    }
    }
    }
    

    View Slide

85. View Controller ʹϩδοΫΛॻ͖ͨ͘ͳ͍
    

    View Slide

86. ViewModel తͳΫϥεΛಋೖ
    

    View Slide

87. UserViewState
    final class UserViewState {
    let id: User.ID
    @Published private(set) var user: User?
    @Published private(set) var iconImage: UIImage?
    init(id: User.ID) {
    self.id = id
    }
    }
    

    View Slide

88. Q6: UserViewState
    UserViewState ʹ loadUser ϝιουΛ௥Ճ͠ɺϢʔβʔ͓Α
    ͼϢʔβʔΞΠίϯΛऔಘ͢ΔίʔυΛ UserViewController
    ͔Β෼཭ͯ͠Լ͍͞ɻ UserViewController ʹ͸
    UserViewState ܕͷ state ϓϩύςΟΛ࣋ͨͤɺ state ͷঢ়
    ଶΛ View ʹ൓ө͢ΔΑ͏ʹͯ͠Լ͍͞ɻͳ͓ɺ͜ͷ໰୊͸ Actor
    ʹؔ܎͋Γ·ͤΜɻ
    !
    state.user Ͱ͸ͳ͘ state.$user ͱॻ͘͜ͱͰɺ user Λ
    Publisher ͱͯ͠औಘ͢Δ͜ͱ͕Ͱ͖·͢ɻ
    

    View Slide

89. Q6: ղ౴ྫ
    

    View Slide

90. loadUser Λฒߦʹݺͼग़ͯ͠΋େৎ෉͔ʁ
    

    View Slide

91. loadUser Ͱى͜ΓಘΔσʔλڝ߹
    let data = try await downloadData(from: url)
    let user = try JSONDecoder().decode(User.self, from: data)
    self.user = user // ͕͜͜ಉ࣌ʹ࣮ߦ͞ΕΔͱʁ
    

    View Slide

92. UserViewState Λ actor ʹ͍ͨ͠
    

    View Slide

93. Q7: actor UserViewState
    UserViewState Λ Actor ʹͯ͠Լ͍͞ɻ
    

    View Slide

94. Q7: ղ౴ྫ
    

    View Slide

95. Swi$ Concurrency Λ࢖ͬͯ
    Publisher ΛߪಡͰ͖Δ
    

    View Slide

96. Publisher.values 5
    for await value in publisher.values {
    ...
    }
    5 h$ps:/
    /developer.apple.com/documenta6on/combine/publisher/values-1dm9r
    

    View Slide

97. AsyncSequence 6
    protocol AsyncSequence {
    associatedtype AsyncIterator: AsyncIteratorProtocol
    where AsyncIterator.Element == Element
    associatedtype Element
    func makeAsyncIterator() -> AsyncIterator
    }
    protocol AsyncIteratorProtocol {
    associatedtype Element
    mutating func next() async throws -> Element?
    }
    6 h$ps:/
    /github.com/apple/swi6-evolu9on/blob/main/proposals/0298-asyncsequence.md
    

    View Slide

98. Q8: Publisher.values
    UserViewState ͷ user ΍ iconImage ͷߪಡΛɺ for await
    Λ࢖͏ܗͰॻ͖׵͑ͯԼ͍͞ɻ
    

    View Slide

99. Q8: ղ౴ྫ
    

    View Slide

100. await state ͷ await ͕ᓔಃ͍͠
     for await user in await state.$user.values {
     ...
     }
     

     View Slide

101. state ͷΩϡʔ͕ϝΠϯΩϡʔͳΒɾɾɾ
     

     View Slide

102. ܕΛ௒͑ͯΩϡʔͰอޢ͍ͨ͠
     

     View Slide

103. Global Actor 7
     7 h$ps:/
     /github.com/apple/swi6-evolu9on/blob/main/proposals/0316-global-actors.md
     

     View Slide

104. MainActor 8
     8 h$ps:/
     /github.com/apple/swi6-evolu9on/blob/main/proposals/0316-global-actors.md#the-main-actor
     

     View Slide

105. @MainActor
     @MainActor func foo() { // isolated
     // ϝΠϯεϨου
     }
     @MainActor ͕෇༩͞Εͨؔ਺΍ϝιουɺϓϩύςΟ౳͸
     MainActor ʹ actor-isolated
     

     View Slide

106. @MainActor
     @MainActor final class Foo {
     var value: Int = 42 // isolated
     func a() { // isolated
     // ϝΠϯεϨου
     }
     }
     @MainActor ͕෇༩͞ΕͨܕͷϝιουɺϓϩύςΟ౳͸
     MainActor ʹ actor-isolated
     

     View Slide

107. Q9: @MainActor
     UserViewState ʹ @MainActor Λ෇༩ͯ͠ɺ
     UserViewController ͱͷ΍ΓͱΓΛ MainActor ಺ͷॲཧͱ
     ͯ͠ѻ͑ΔΑ͏ʹͯ͠Լ͍͞ɻ
     

     View Slide

108. Q9: ղ౴ྫ
     

     View Slide

109. ObservableObject
     

     View Slide

110. UserViewState Λ ObservableObject ʹ
     final class UserViewState: ObservableObject {
     ...
     }
     

     View Slide

111. UserViewState Λ ObservableObject ʹ
     • Swi%UI ΁ͷҠߦΛݟਾ͑ͯ
     • Computed Property ͸ @Published ʹͰ͖ͳ͍
     

     View Slide

112. UserViewState Λ ObservableObject ʹ
     • user ΍ iconImage Λݸผʹߪಡ͢ΔͷͰ͸ͳ͘ɺ
     objectWillChange9 Λߪಡ͢Δ
     9 h$ps:/
     /developer.apple.com/documenta6on/combine/observableobject/objectwillchange-2oa5v
     

     View Slide

113. Q10: ObservableObject
     UserViewState Λ ObservableObject ʹద߹ͤ͞ɺ user,
     iconImage Λݸผʹߪಡ͢ΔͷͰ͸ͳ͘ɺ objectWillChange
     Λߪಡͯ͠ View ʹ൓ө͢Δܗʹमਖ਼ͯ͠Լ͍͞ɻ
     

     View Slide

114. Q10: ղ౴ྫ
     

     View Slide

115. Q10 Ͱ࣮૷ͨ͠ UserViewState ͸
     Swi(UI Ͱ΋ͦͷ··ར༻Մೳ
     

     View Slide

116. Q11: Swi(UI
     UserViewController ͱಉ༷ͷݟͨ໨ɾڍಈΛ࣮ݱ͢Δ
     UserView Λ Swi%UI Ͱ࣮૷ͯ͠Լ͍͞ɻ
     !
     @StateObject Ͱ UserViewState Λอ࣋͠·͢ɻ
     @StateObject private var state: UserViewState
     

     View Slide

117. Q11: ղ౴ྫ
     

     View Slide