Property Wrapperで遊ぼう / Play with Property Wrapper

帰ってきた関西モバイルアプリ研究会#3 https://kanmoba.connpass.com/event/137475/

Transcript

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

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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 ?
   

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3. ⚠͝஫ҙ
   • ؀ڥ
   • macOS Mojave Version 10.14.6
   • Xcode 11.0 GM seed (11M419c)
   

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4. Property Wrapper
   

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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
   

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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
   

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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
   

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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
   

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9. OSS SwiftͰ͸࣮૷த
   

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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
    

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11. 
    BugΛ୳ͦ͏
    

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12. Property WrapperͷΑ͋͘Δྫ
    

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13. Property Wrapper x UserDefaults
    

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14. Property Wrapper x UserDefaults
    • [WWDC 2019] What's New in Swift
    • https://developer.apple.com/videos/play/wwdc2019/402
    • UserDefaultsΛWrapͯ͠ɺϘΠϥʔϓϨʔτΛ௵͍ͯ͘͠
    

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15. @propertyWrapper
    struct UserDefault {
    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
    

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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
    

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17. defaultValue == nil
    ΋Ͱ͖ͦ͏ͩͳ
    

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18. @propertyWrapper
    struct UserDefault {
    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
    

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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
    

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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
    

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

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24. ͱ͍͏͜ͱͰ
    

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

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

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27. Simple Case
    import Foundation
    var value: Any = "value"
    @propertyWrapper
    struct Wrapper {
    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
    playground.printImplicitlyOptionalType() // Optional
    playground.printNonOptionalType() // String
    

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28. ·ͱΊ
    

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29. ·ͱΊ
    • Property WrapperΛ࢖͍౗ͯ͠ɺόάใࠂΛ͍ͯ͜͠͏
    

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30. &OKPZ1SPQFSUZ8SBQQFS 5IBOLT
    w NVUBZVUBSP!HNBJMDPN
    w IUUQTUXJUUFSDPNZVUBJMBOH
    w IUUQTHJUIVCDPNZVUBJMBOH
    

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