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Function Builders in Swift 5.1
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LINE Developers
June 25, 2019
Technology
1
370
Function Builders in Swift 5.1
Christopher Rogers
WWDC19 Recap at LINE
https://line.connpass.com/event/134346/
LINE Developers
June 25, 2019
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Transcript
Function Builders in Swift 5.1 Christopher Rogers Twitter: @christorogers /
GitHub: @ChristopherRogers
Function Builder ͱʁ ؔΛϏϧμʔߏจʹมߋͰ͖Δ৽ػೳ1 • Embedded Domain-Specific Language (eDSL) •
SwiftUI ͷͨΊʁ • GM·ͰมΘΔՄೳੑ͕ߴ͍ 1 https://forums.swift.org/t/function-builders/25167
var body: some View { HStack { Image(uiImage: profile.image) Spacer()
Text(profile.name) } }
var body: some View { /* return লུ */ HStack
{ // ͔͜͜Β͕ function builder ߏจ Image(uiImage: profile.image) Spacer() Text(profile.name) } } public HStack { public init(@ViewBuilder _ content: () -> Content) }
var body: some View { /* return লུ */ HStack
{ // ͔͜͜Β͕ function builder ߏจ Image(uiImage: profile.image) Spacer() Text(profile.name) } }
var body: some View { /* return লུ */ HStack
{ // ͔͜͜Β͕ function builder ߏจ let _v0 = Image(uiImage: profile.image) let _v1 = Spacer() let _v2 = Text(profile.name) return ViewBuilder.buildBlock(_v0, _v1, _v2) } }
• ܕΛఆٛ͢Δ • ܕͷએݴΛ @_functionBuilder Ͱम০͢Δ • ಛఆͷϝιουΛ࣮͢Δ • ४ڌ͢Δ
protocol ͳ͍ • ʢݱ࣌Ͱʣϝιουͯ͢ static • ҾͱฦΓͷܕ͋Δఔࣗ༝ • ਂ͞༏ઌ୳ࡧͰࣜΛධՁͯ͠ม͍ͯ͘͠ @_functionBuilder public struct ViewBuilder { public static func buildBlock<Content>(_ content: Content) -> Content where Content: View }
buildBlock • །Ұඞਢͷϝιου • จʢ{}Λͬͨͱ͜Ζʣ୯ҐͰม͢Δ • ͯ͢ͷࣜΛ·ͱΊͯҾͱͯ͠ड͚औΔ • ՄมҾ •
ϝιου overload Ͱෳ࣮ let _v0 = Image(uiImage: profile.image) let _v1 = Spacer() let _v2 = Text(profile.name) return ViewBuilder.buildBlock(_v0, _v1, _v2)
buildExpression • ࣜ୯ҐͰม͢Δ͜ͱ͕Մೳ • ݱࡏར༻ෆՄ let _v0 = ViewBuilder.buildExpression(Image(uiImage: profile.image))
let _v1 = ViewBuilder.buildExpression(Spacer()) let _v2 = ViewBuilder.buildExpression(Text(profile.name)) return ViewBuilder.buildBlock(_v0, _v1, _v2)
buildOptional • ࣮͢Ε if จ͕͑ΔΑ͏ʹͳΔ • Ҿ Optional ܕʹ͢Δඞཁ͕͋Δ •
ϝιου໊ʹ͍ͭͯٞத • beta 2 Ͱڍಈ͕༷ͱҟͳΔ
if isEnabled { "hoge" } else { 42 }
var _v0Opt: String? var _v1Opt: Int? if isEnabled { _v0
= "hoge" } else { _v1 = 42 } let _v0 = MyBuilder.buildOptional(_v0Opt) let _v1 = MyBuilder.buildOptional(_v1Opt)
buildEither • ݅ʹΑΒͣܕΛ֬ఆ͢Δ͜ͱ͕Ͱ͖Δ • first/second ύϥϝʔλϥϕϧͰذ͕ද͞ΕΔ • ݱࡏར༻ෆՄ let _v0:
String if languageCode == "ja" { _v0 = MyBuilder.buildEither(first: "hoge") } else if languageCode == "en" { _v0 = MyBuilder.buildEither(second: MyBuilder.buildEither(first: "foo")) } else { _v0 = MyBuilder.buildEither(second: MyBuilder.buildEither(second: "")) }
ͦͷଞͷϝιου buildDo • do จͰಛఆͷڍಈΛಋೖ͢Δ߹ʹ༻͍Δ • buildBlockͷΘΓʹݺΕΔ buildFunction • ฦΓͷܕΛ࠷ޙʹม͢Δ߹ʹ༻͍Δ
• Ұ൪࠷ޙʹbuildBlockͷΘΓʹݺΕΔ
ޚਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠