Property Wrapperで遊ぼう / Play with Property Wrapper

Transcript

1. Property WrapperͰ༡΅͏ 2019/09/11 @ؼ͖ͬͯͨؔ੢ϞόΠϧΞϓϦݚڀձ#3 Yutaro Muta @yutailang0119

2. • Yutaro Muta @yutailang0119 • Hatena Co., Ltd. @Kyoto •

   Conference Staff • builderscon 2017, 2018, 2019 • try! Swift Tokyo 2019, 2020 • try! Swift Tokyo 2020 νέοτൢച։࢝ • https://www.tryswift.co/events/2020/tokyo/en/ Who am I ?

3. ⚠͝஫ҙ • ؀ڥ • macOS Mojave Version 10.14.6 • Xcode

   11.0 GM seed (11M419c)

4. Property Wrapper

5. Property Wrapper • https://github.com/apple/swift-evolution/blob/master/proposals/0258-property- wrappers.md • ࠷ॳͷPitch͸Property Delegateͱͯ͠ɺMarch 3, 2019ʹొ৔

   • https://forums.swift.org/t/returned-for-revision-se-0258-property-delegates/24080 • Swift 5.1 ~ • ొ৔౰ॳ͸Swift 5.1ʹೖΒͳ͍ͩΖ͏ͱ͍͏ҹ৅͕ͩͬͨɺWWDCͰApple͕ൃදͨ͠ SwiftUIʹ΋࢖༻͞Ε͍ͯΔ • Swift 5.1ͷfinal branching͸March 18, 2019

6. Property Wrapper • https://github.com/apple/swift-evolution/blob/master/proposals/0258-property- wrappers.md • ࠷ॳͷPitch͸Property Delegateͱͯ͠ɺMarch 3, 2019ʹొ৔

   • https://forums.swift.org/t/returned-for-revision-se-0258-property-delegates/24080 • Swift 5.1 ~ • ొ৔౰ॳ͸Swift 5.1ʹೖΒͳ͍ͩΖ͏ͱ͍͏ҹ৅͕ͩͬͨɺWWDCͰApple͕ൃදͨ͠ SwiftUIʹ΋࢖༻͞Ε͍ͯΔ • Swift 5.1ͷfinal branching͸March 18, 2019

7. https://github.com/apple/swift-evolution/blob/master/ proposals/0258-property-wrappers.md https://github.com/apple/swift-evolution/blob/master/proposals/0258-property-wrappers.md

8. https://github.com/apple/swift-evolution/blob/master/ proposals/0258-property-wrappers.md https://github.com/apple/swift-evolution/blob/master/proposals/0258-property-wrappers.md

9. OSS SwiftͰ͸࣮૷த

10. ࣮૷ঢ়گ • େ࿮͸Ͱ͖͍ͯΔ • https://github.com/apple/swift/pulls?utf8=✓&q=is%3Apr+SE-+0258 • όάใࠂ΋͔ͳΓ͋Δ • https://bugs.swift.org/issues/?jql=labels+%3D+PropertyWrappers

11. BugΛ୳ͦ͏

12. Property WrapperͷΑ͋͘Δྫ

13. Property Wrapper x UserDefaults

14. Property Wrapper x UserDefaults • [WWDC 2019] What's New in

    Swift • https://developer.apple.com/videos/play/wwdc2019/402 • UserDefaultsΛWrapͯ͠ɺϘΠϥʔϓϨʔτΛ௵͍ͯ͘͠

15. @propertyWrapper struct UserDefault<T> { let key: String let defaultValue: T

    init(_ key: String, defaultValue: T) { self.key = key self.defaultValue = defaultValue UserDefaults.standard.register(defaults: [key: defaultValue]) } var wrappedValue: T { get { return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue } set { UserDefaults.standard.set(newValue, forKey: key) } } } Property Wrapper x UserDefaults

16. @UserDefault("USES_TOUCH_ID", defaultValue: false) static var usesTouchID: Bool @UserDefault("LOGGED_IN", defaultValue: false)

    static var isLoggedIn: Bool if !isLoggedIn && usesTouchID { !authenticateWithTouchID() } Property Wrapper x UserDefaults

17. defaultValue == nil ΋Ͱ͖ͦ͏ͩͳ

18. @propertyWrapper struct UserDefault<T> { let key: String let defaultValue: T

    init(_ key: String, defaultValue: T) { self.key = key self.defaultValue = defaultValue } var wrappedValue: T { get { return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue } set { UserDefaults.standard.set(newValue, forKey: key) } } } Property Wrapper x UserDefaults x Optional

19. @UserDefault("USES_TOUCH_ID", defaultValue: nil) static var usesTouchID: Bool @UserDefault("LOGGED_IN", defaultValue: false)

    static var isLoggedIn: Bool if !isLoggedIn && usesTouchID { !authenticateWithTouchID() } Property Wrapper x UserDefaults x Optional

20. @UserDefault("USES_TOUCH_ID", defaultValue: nil) static var usesTouchID: Bool @UserDefault("LOGGED_IN", defaultValue: false)

    static var isLoggedIn: Bool if !isLoggedIn && usesTouchID { !authenticateWithTouchID() } Property Wrapper x UserDefaults x Optional
21. None

22. @UserDefault("USES_TOUCH_ID", defaultValue: nil) static var usesTouchID: Bool print(type(of: usesTouchID)) //

    Optional<Bool> ܕΛݟͯΈΔ
23. None

24. ͱ͍͏͜ͱͰ

25. https://bugs.swift.org/browse/SR-11443

26. SR-11443 Property Wrapper overwrites type declaration • bugs swiftʹग़ͨ͠

27. Simple Case import Foundation var value: Any = "value" @propertyWrapper

    struct Wrapper<Value> { private let defaultValue: Value init(defaultValue: Value) { self.defaultValue = defaultValue } var wrappedValue: Value { get { (value as? Value) ?? defaultValue } set { value = newValue } } } final class Playground { @Wrapper(defaultValue: nil) var explicitlyOptional: String? @Wrapper(defaultValue: nil) var implicitlyOptional: String @Wrapper(defaultValue: "NonOptional") var nonOptional: String func printExplicitlyOptionalType() { print(type(of: self.explicitlyOptional)) } func printImplicitlyOptionalType() { print(type(of: self.implicitlyOptional)) } func printNonOptionalType() { print(type(of: self.nonOptional)) } } let playground = Playground() playground.printExplicitlyOptionalType() // Optional<String> playground.printImplicitlyOptionalType() // Optional<String> playground.printNonOptionalType() // String

28. ·ͱΊ

29. ·ͱΊ • Property WrapperΛ࢖͍౗ͯ͠ɺόάใࠂΛ͍ͯ͜͠͏

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