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if 式と switch 式による SwiftUI のプレビューエラー対策
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ojun
November 14, 2023
Programming
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1.9k
if 式と switch 式による SwiftUI のプレビューエラー対策
ojun
November 14, 2023
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Transcript
potatotips #85 iOS/Android։ൃTipsڞ༗ձ 2023/11/14 @Voicy if ࣜͱ switch ࣜʹΑΔ SwiftUI
ͷϓϨϏϡʔΤϥʔରࡦ ojun - DeNA Co., Ltd.
ࣗݾհʢojunʣ • name: ojun • 2023৽ଔೖࣾ • iOSΤϯδχΞ @ojun_9
Xcode 15 ରԠਐΜͰ͍·͔͢ʁ
Xcode 15.0 Asset Catalogs / String Catalogs PreviewϚΫϩ Swift 5.9
ϒοΫϚʔΫػೳ ɾෳͷݴޠػೳͷՃ ɾσόοά࣌ʹมͷ༰Λग़ྗ͢ΔͨΊʹར༻͢ΔpίϚϯυͱpoίϚϯυ ʹΑΔग़ྗ͕࣌ؒେ෯ʹॖ ͦͷଞ͍Ζ͍Ζ
Xcode 15.0 Asset Catalogs / String Catalogs PreviewϚΫϩ Swift 5.9
ϒοΫϚʔΫػೳ ɾෳͷݴޠػೳͷՃ ͦͷଞ͍Ζ͍Ζ ɾσόοά࣌ʹมͷ༰Λग़ྗ͢ΔͨΊʹར༻ՄೳͳpίϚϯυͱpoίϚϯυ ʹΑΔग़ྗ͕࣌ؒେ෯ʹॖ
Swift 5.9: if ͱ switch ͷࣜදݱ
Swift 5.9: ifͱswitchͷࣜදݱ Swift 5.9͔ΒswitchͱifΛࣜͱͯ͠දݱͰ͖ΔΑ͏ʹͳͬͨ
Swift 5.9: ifͱswitchͷࣜදݱ Swift 5.9͔ΒswitchͱifΛࣜͱͯ͠දݱͰ͖ΔΑ͏ʹͳͬͨ
Swift 5.9: ifͱswitchͷࣜදݱ Swift 5.9͔ΒswitchͱifΛࣜͱͯ͠දݱͰ͖ΔΑ͏ʹͳͬͨ
Swift 5.9: ifͱswitchͷࣜදݱ Swift 5.9͔ΒswitchͱifΛࣜͱͯ͠දݱͰ͖ΔΑ͏ʹͳͬͨ
Swift 5.9: ifͱswitchͷࣜදݱ Swift 5.9͔ΒswitchͱifΛࣜͱͯ͠දݱͰ͖ΔΑ͏ʹͳͬͨ
Preview࣌ʹར༻͢Δ
Preview࣌ʹར༻͢Δ isSwiftͷBoolʹج͍ͮͯTextΛฦ͢
Preview࣌ʹར༻͢Δ isSwiftͷBoolʹج͍ͮͯTextΛฦ͢ ௨ৗͷϏϧυ 🎉 ͳ͘ޭ͢Δ
Preview࣌ʹར༻͢Δ isSwiftͷBoolʹج͍ͮͯTextΛฦ͢ ௨ৗͷϏϧυ 🎉 ͳ͘ޭ͢Δ Preview࣌ͷϏϧυ 😭 ίϯύΠϧΤϥʔ͕ൃੜ͢Δ
Preview࣌ʹར༻͢Δ isSwiftͷBoolʹج͍ͮͯTextΛฦ͢ ௨ৗͷϏϧυ 🎉 ͳ͘ޭ͢Δ Preview࣌ͷϏϧυ 😭 ίϯύΠϧΤϥʔ͕ൃੜ͢Δ Preview ProviderΛར༻ͯ͠ಉ༷
Preview࣌ʹར༻͢Δ 'if' may only be used as expression in return,
throw, or as the source of an assignment
ղܾํ๏
ղܾํ๏ 1. @ViewBuilderΩʔϫʔυΛ༩͢Δ 2. Opaque typeͰͳ͍໌֬ͳܕΛฦ͢ 3. Opaque Type Λ
Existential Type ʹஔ͖͑Δ
@ViewBuilderΩʔϫʔυΛ༩͢Δ @ViewBuilderΩʔϫʔυΛ༩͢Δ ͜ͱͰPreview࣌ͷΤϥʔΛճආͰ͖Δ ௨ৗͷϏϧυ 🎉 ͳ͘ޭ͢Δ Preview࣌ͷϏϧυ 🎉 ͳ͘ޭ͢Δ
໌֬ͳܕΛฦ͢ ௨ৗͷϏϧυ 🎉 ͳ͘ޭ͢Δ Preview࣌ͷϏϧυ 🎉 ͳ͘ޭ͢Δ `Text`ͷΑ͏ʹܕΛ໌֬ʹ͢Δ ͜ͱͰPreview࣌ͷΤϥʔΛճආͰ͖Δ
Opaque Type Λ Existential Type ʹஔ͖͑Δ ΓΛany Viewʹ͢Δํ๏ ͨͩ͠ɺݺͼग़͠ݩͰܕΩϟετΛ ߦ͏ඞཁ͕͋Δ
௨ৗͷϏϧυ 🎉 ͳ͘ޭ͢Δ Preview࣌ͷϏϧυ 🎉 ͳ͘ޭ͢Δ
ͷݪҼΛߟ͢Δ ʢࠜຊݪҼಥ͖ࢭΊΒΕ·ͤΜͰͨ͠😢ʣ
ͷݪҼΛߟ͢Δ ContentView.1.preview-thunk.swift ͱ͍͏ϑΝΠϧ͕ҎԼʹଘࡏ͢Δ ~/Library/Developer/Xcode/DerivedData/MakeViewFromSwitch- fghepcludbkyehbmhgmucvzdrxsk/Build/Intermediates.noindex/Previews/ MakeViewFromSwitch/Intermediates.noindex/MakeViewFromSwitch.build/ Debug-iphonesimulator/MakeViewFromSwitch.build/Objects-normal/arm64
ContentViewͷPreviewϏϧυ͕Δͱ͜ͷϑΝΠϧ͕ߋ৽͞ΕΔ
ྫ͑ɺany ErrorΛฦ͢Α͏ͳϝιουΛ࣮͢Δͱ
ContentView.1.preview-thunk.swift ߋ৽͞ΕΔ
ΓΛOpaque Typeʹ͢Δͱ ͨͩ͠
ContentView.1.preview-thunk.swift ͔ΒgetErrorͷॲཧ͕ফ͑Δ
ͷݪҼΛߟ͢Δ ίϯύΠϧΤϥʔʹͳ࣮ͬͨ Opaque Typeͩͬͨ తͳݪҼ͔Θ͔Βͳ͍͕͜Ε͕ ʹͳ͍ͬͯΔՄೳੑ͕͋Δ
·ͱΊ Swift 5.9͔Β if ͱ switch Λࣜͱͯ͠ѻ͑ΔΑ͏ʹͳͬͨ if / switch
ࣜΛ༻͍ͯSwiftUIͷViewΛʢopaque typeͱͯ͠ʣฦ͢ͱ Preview࣌ͷϏϧυͰͷΈίϯύΠϧΤϥʔ͕ൃੜ͢Δ ҎԼͷ͍ͣΕ͔ͷํ๏ͰͷରԠΛ͢Δ͜ͱ͕Ͱ͖Δ 1. @ViewBuilderΩʔϫʔυΛ༩͢Δ 2. Opaque typeͰͳ͍໌֬ͳܕΛฦ͢ʢText ͳͲʣ 3. Opaque Type Λ Existential Type ʹஔ͖͑Δ
͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ