Voidと() - 意図を伝える“ユニット型”の世界- / Void vs () -The World of Expressing Intent

2025.09.30 チキチキ！モバイルLT大会 〜残暑編〜

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1. Voidͱ() - ҙਤΛ఻͑Δ“Ϣχοτܕ”ͷੈք- STORESגࣜձࣾ ϞόΠϧ։ൃຊ෦ Ϛωʔδϟʔ/iOSΤϯδχΞ ௕୩઒ ক࢘ʢ@marcy731ʣ 2025.09.30 νΩνΩʂϞόΠϧLTେձ ʙ࢒ॵฤʙ
2. Void
6. public typealias Void = ()
7. Void ͸ () ͷܕΤΠϦΞε public typealias Void = ()
8. ()
9. () : “ۭͷλϓϧ஋”
10. () : “Empty Tuple”
11. Tuple • ෳ਺ͷ஋Λͻͱ·ͱΊʹͰ͖Δߏ଄ • ܕͱͯ͠͸ʮҟͳΔܕΛͻͱͭʹଋͶͨ߹੒ܕ (product type)ʯ
12. let tuple1: (Int, String) = (42, “hello") let tuple2: (id: Int, name: String) = (id: 1, name: "Alice") ཁૉʹॱং͕͋Γɺ0͔ΒͷΠϯσοΫε΍ϥϕϧͰΞΫηεͰ͖Δ Tuple
13. let tuple1: (Int, String) = (42, “hello") let tuple2: (id: Int, name: String) = (id: 1, name: "Alice") ϥϕϧΛ෇͚Ε͹ʮߏ଄ମʯͬΆ͘ѻ͑Δ Tuple
14. 0ཁૉλϓϧ: () → ۭλϓϧɺ།Ұͷ஋͔͠ͳ͍ → Ϣχοτܕ 1ཁૉλϓϧ: ଘࡏ͠ͳ͍ʢ(Int) = Int ʹ௵ΕΔʣ 2ཁૉҎ্λϓϧ: (A, B, ...) ͱͯ͠ී௨ʹ࢖͑Δ λϓϧͷཁૉ਺͝ͱͷಛҟੑ
15. 0ཁૉλϓϧ: () → ۭλϓϧɺ།Ұͷ஋͔͠ͳ͍ → Ϣχοτܕ 1ཁૉλϓϧ: ଘࡏ͠ͳ͍ʢ(Int) = Int ʹ௵ΕΔʣ 2ཁૉҎ্λϓϧ: (A, B, ...) ͱͯ͠ී௨ʹ࢖͑Δ λϓϧͷཁૉ਺͝ͱͷಛҟੑ Void
16. public typealias Void = ()
17. public typealias Void = () Ϣχοτܕͱͯ͠ͷ ()
18. ΫϩʔδϟͰͷҙਤදݱ let f: () -> Void = { } let g: () -> () = { }
19. ΫϩʔδϟͰͷҙਤදݱ let f: () -> Void = { } let g: () -> () = { } ܕγεςϜ্·ͬͨ͘ಉ͡ܕɻ ݺͼग़͠ํɾಈ࡞ʹҧ͍͸ͳ͍ɻ
20. ΫϩʔδϟͰͷҙਤදݱ let f: () -> Void = { } let g: () -> () = { } Ͱ΋χϡΞϯε͸ҧ͏ɻ
21. () -> Void let f: () -> Void = { } • ҙຯ߹͍: ʮ෭࡞༻͚ͩΛߦ͍ɺ໭Γ஋͸ͳ͍ʯ • ϝϦοτ: • ׳शతʹ࠷΋޿͘࢖ΘΕ͍ͯΔ • ඪ४ϥΠϒϥϦ΍ެࣜυΩϡϝϯτͰ΋ͪ͜Β͕جຊ • ʮฦ͢஋͸ͳ͍ʯͱ͍͏ҙਤ͕ଈ఻ΘΔʢಡΈ΍͍͢ʣ • ࣮຿తഎܠ: • νʔϜશମͰಡΜͩͱ͖ʹ Ұ؏ੑ͕͋Δ • ެࣜʹ฿͏ͷ͕ʮSwiftyʯͳॻ͖ํ • ܕͷཪଆʢۭλϓϧͷਖ਼ମʣΛҙࣝ͠ͳͯ͘΋Α͍ͨΊɺແବʹಡऀΛ໎Θͤͳ͍
22. () -> () let g: () -> () = { } • ҙຯ߹͍: ʮۭλϓϧʢ།Ұͷ஋ʣΛฦ͢ʯ͜ͱΛ ͋Γͷ··ॻ͍ͨܗ • ϝϦοτ: • ܕཧ࿦ʹ͍ۙදهͰɺਖ਼͕֬͋͞Δ • σϝϦοτ: • ࣮຿Ͱ͸΄ͱΜͲݟ͔͚ͳ͍ → ಡΈख͕ʮͳΜͰͬͪ͜ʹͨ͠ΜͩΖ͏ʁʯͱҰॠ ߟ͑Δ • Ұൠతͳ Swift ίʔυελΠϧ͔Β֎ΕΔ → ʮSwifty ͡Όͳ͍ʯͱײ͡ΒΕ΍͍͢
23. APIઃܭͰͷ׆༻ 1. Result<Void, Error> 2. Optional<Void> 3. Reactive / Combine
24. Result<Void, Error> ʮ੒ޭ͕ͩฦ͢஋͸ͳ͍ʯ func save(document: Data) async -> Result<Void, SaveError> { // ... do work guard hasSpace else { return .failure(.diskFull) } // อଘ੒ޭɻฦ͢σʔλ͸ແ͍ͷͰ Voidʢʹ()ʣ return .success(()) }
25. Optional<Void> ʮBool ͩͱԿͷਅِ͔͕ᐆດɻVoid? ͸׬ྃͱ͍͏ग़དྷࣄΛܕͰදݱʯ private var presented: Void? = nil func presentIfNeeded() { guard presented == nil else { return } // طʹ࣮ߦࡁΈ presentOnboardingUI() presented = () // ࣮ߦࡁΈͷࠟ੻Λه࿥ }
26. Reactive / Combine ʮ“Πϕϯτ͕ى͖ͨ”͚ͩΛ఻͑Δʯ final class ViewModel { let didTap = PassthroughSubject<Void, Never>() // ஋ͳ͠Πϕϯτ func onButtonTap() { didTap.send(()) // Voidܕͷ஋͸ () ΛૹΔ } }
27. Neverͱͷରൺ func log() -> Void { } // ݺΜͩΒ໭Δ func crash() -> Never { fatalError() } // ݺΜͩΒ໭Βͳ͍
28. ͳͥ () -> () ͸࣮຿Ͱ͸͋·Γݟ͔͚ͳ͍ͷ͔ʁ 1. ՄಡੑॏࢹͷจԽɿ() -> Void ͷํ͕௚ײత 2. ެࣜAPIɾυΩϡϝϯτͷӨڹɿAppleඪ४ϥΠϒϥϦ͸Ұ؏ͯ͠ Void 3. ʮSwiftyʯ͞ͷ௥ٻɿSwiftจԽ͸ʮಡΈ΍͢͞ɾ׳शʯΛ༏ઌ 1. () -> Void = Swifty 2. () -> () = ਖ਼͍͚͠ͲҰॠҾ͔͔ͬΔ
29. ·ͱΊ 1. ܕ͸υΩϡϝϯτҎ্ʹ༤ห 1. Void / () ͷ࢖͍෼͚͕ APIઃܭͰҙਤΛ఻͑ΔखஈʹͳΔ 2. Result<Void, Error> ΍ Optional<Void> Ͱʮແʯ΋ܕʹͰ͖Δ 3. Never ͱͷରൺͰʮฦ͞ͳ͍ʯͱʮฦͤͳ͍ʯ͕໌֬ʹ۠ผͰ͖Δ 4. ࣋ͪؼΓ: ʮ໭Γ஋ͳ͠ʯΛܰࢹͤͣɺܕͰҙਤΛਖ਼͘͠఻͑Α͏
30. ܕϓϩάϥϛϯάྑ͍