Swi$ ؛઒ࠀݾ @k_katsumi Yuta Koshizawa @koher

؛઒ࠀݾ @k_katsumi Apple ޷͖͕ߴͯ͡ iOS ΞϓϦέʔγϣ ϯͷ։ൃΛ 14 ೥ଓ͚͍ͯ·͢ɻझຯͰ ࡞͍ͬͯΔ OSS ϥΠϒϥϦ͸͚ͬ͜͏ਓ ؾ͕͋Γ·͢ɻ Yuta Koshizawa @koher "Heart of Swi-" Λॻ͖·ͨ͠ɻීஈ͸ओ ʹϦΞϧλΠϜը૾ॲཧΛ༻͍ͨ iOS Ξ ϓϦΛ։ൃ͍ͯ͠·͢ɻ

Swi$ ͷ࠷৽ಈ޲

Swi$ 5.5: 9 ݄ϦϦʔεʢʁʣ

Concurrency ʢฒߦॲཧʣ

Swi$ 5.5+ ͷ Concurrency ฒߦॲཧʹىҼ͢Δσʔλڝ߹΍σουϩοΫ͕ى͜Βͳ͍͜ͱ ΛίϯύΠϥ͕อূͯ͘͠ΕΔɻ

Ұݟ Ruby ΍ Python ͷΑ͏͚ͩͲɾɾɾ // 0 Ҏ্ 100 ະຬͷ੔਺ͷ߹ܭ var sum = 0 for i in 0 ..< 100 { sum += i } print(sum)

ίϯύΠϥ͕ΨνΨνʹ੩తݕࠪ͢Δݴޠ • Null Safety ʢ 2014 ೥ͷϦϦʔε౰ॳ͔Βʣ • throws/try ʢݕࠪྫ֎ͷΑ͏ͳ΋ͷʣ

ίϯύΠϥ͕ΨνΨνʹ੩తݕࠪ͢Δݴޠ • Null Safety ʢ 2014 ೥ͷϦϦʔε౰ॳ͔Βʣ • throws/try ʢݕࠪྫ֎ͷΑ͏ͳ΋ͷʣ • σʔλڝ߹ͱσουϩοΫͷ๷ࢭ

Swi$ ͷฒߦॲཧ ! async/await " Structured Concurrency # actor

! async/await

async/await ͷྫ // Swift func fetchUser(...) async -> User { let userData = await downloadData(...) ... return user } Ұݟ JavaScript ౳ͷ async/await ͱࣅ͍ͯΔɻ

JS/TS ͷ async/await ͱͷҧ͍ // TypeScript async function fetchUser(...): Promise { const userData = await downloadData(...); ... return user; } JS/TS Ͱ͸ async ؔ਺͸ Promise Λฦ͢ɻ

JS/TS ͷ async/await ͱͷҧ͍ // Swift func fetchUser(...) async -> User { let userData = await downloadData(...) ... return user } Swi$ ͷ async ؔ਺͸ Promise Λฦ͞ͳ͍ɻ

JS/TS ͷ async/await ͱͷҧ͍ // TypeScript async function fetchUser(...): Promise { const promise = downloadData(...); ... return user; } JS/TS Ͱ͸ await ͠ͳ͍ͱ Promise ΛಘΔɻ

JS/TS ͷ async/await ͱͷҧ͍ // Swift func fetchUser(...) async -> User { let userData = downloadData(...) // ίϯύΠϧΤϥʔ ... return user } Swi$ Ͱ͸ await ͠ͳ͍ͱίϯύΠϧΤϥʔɻඞͣ await ͞ΕΔ ͷͰ Promise ʹ૬౰͢Δ΋ͷ͸ͳ͍ɻ

await ඞਢͳͷͰ await ๨Ε͕ى͜Βͳ͍ func updateUser(user: User) async { // ⛔ ίϯύΠϧΤϥʔ db.collection("users") .document(user.id) .setData(from: user) } ʢಛʹ໭Γ஋͕ͳ͍৔߹Ͱ΋ʣҙਤͤͣ await Λ෇͚๨ΕΔࣄނ ͕ى͜Βͳ͍ɻ

JS/TS Ͱ͸ Promise Λ׆༻ͯ͠ฒߦʹ࣮ߦ // TypeScript async function fetchUser(...): Promise { const userPromise = downloadData(...); const avatarPromise = downloadData(...); const [userData, avatarData] = await Promise.all([userPromise, avatarPromise]); ... return user; } await ͠ͳ͍͜ͱ͕Մೳͩͱෳ਺ͷඇಉظॲཧΛฒߦʹ࣮ߦͰ͖ Δɻ

await ඞਢͰ Promise ͕ͳ͍ͳΒෳ਺ͷ ඇಉظॲཧΛͲ͏΍ͬͯฒߦʹ࣮ߦ͢Δʁ

! Structured Concurrency

async let Ͱฒߦॲཧ // Swift func fetchUser(...) async -> User { async let userData = downloadData(...) async let avatarData = downloadData(...) let user = await User(data: userData, avatar: avatarData) return user }

JS/TS ͷ৔߹ // TypeScript async function fetchUser(...): Promise { const userPromise = downloadData(...); const avatarPromise = downloadData(...); const [userData, avatarData] = await Promise.all([userPromise, avatarPromise]); ... return user; }

async let Ͱฒߦॲཧ // Swift func fetchUser(...) async -> User { async let userData = downloadData(...) async let avatarData = downloadData(...) let user = await User(data: userData, avatar: avatarData) return user } async let ͸ Promise ͱҧͬͯείʔϓͷ֎ʹ࣋ͪग़ͤͳ͍ɻ

Structured Concurrency ߏ଄Խϓϩάϥϛϯάʢ Structured Programming ʣͰ͸ goto Ͱ είʔϓ͔Β୤ग़Ͱ͖ͳ͍Α͏ʹɺ async let ͸ඞͣείʔϓ ͷதͰղܾ͞ΕΔɻ

Structured Concurrency ͷԿ͕͏Ε͍͠ͷ͔?

ྫ: ඇಉظॲཧͷΩϟϯηϧ

async ؔ਺ͷݺͼग़͠ͷ੍໿ func foo() async -> Int { ... } func bar() async -> Int { await foo() * 2 // ✅ OKɹ } async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺ΂ͳ͍ɻ

async ؔ਺ͷݺͼग़͠ͷ੍໿ func foo() async -> Int { ... } func bar() -> Int { await foo() * 2 // ⛔ ίϯύΠϧΤϥʔ } async ؔ਺͸ async ؔ਺ͷதͰ͔͠ݺ΂ͳ͍ɻ

Task Task({ await foo() }) async ؔ਺ͷݺͼग़͠ͷେݩ͸ Task ͷίϯετϥΫλʢΠχ γϟϥΠβʣɻ͢΂ͯͷ async ؔ਺͸ Task ͷ্Ͱ࣮ߦ͞ΕΔɻ

Child Task Task({ async let a = foo() // Child Task: foo async let b = bar() // Child Task: bar print(await a + b) }) async let Ͱ͸ฒߦʹ࣮ߦ͞ΕΔ Child Task ͕࡞ΒΕΔɻߏ଄Խ ͞Ε͍ͯΔͷͰ Task ͸πϦʔΛ࡞Δɻ

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ඇಉظॲཧͷΩϟϯηϧ let task = Task({ async let a = foo() async let b = bar() print(try await a + b) }) task.cancel() Task Λ cancel ͢Δͱ Task πϦʔશମ͕ҰׅΩϟϯηϧ͞Ε ΔɻඇಉظॲཧͷΩϟϯηϧΛѻ͍΍͍͢ɻ

! actor

σʔλڝ߹ͱσουϩοΫͷ๷ࢭ

σʔλڝ߹ͷྫ class Counter { var count: Int = 0 func increment() -> Int { count += 1 return count } }

Χ΢ϯλʹฒߦʹΞΫηε͢Δ৔߹ let counter = Counter() Task { print(counter.increment()) // ? } Task { print(counter.increment()) // ? }

Χ΢ϯλʹฒߦʹΞΫηε͢Δ৔߹ let counter = Counter() Task { print(counter.increment()) // 1 } Task { print(counter.increment()) // 2 }

Χ΢ϯλʹฒߦʹΞΫηε͢Δ৔߹ let counter = Counter() Task { print(counter.increment()) // 2 } Task { print(counter.increment()) // 1 }

Χ΢ϯλʹฒߦʹΞΫηε͢Δ৔߹ let counter = Counter() Task { print(counter.increment()) // 2 } Task { print(counter.increment()) // 2 } ྆ํͷΠϯΫϦϝϯτ͕ߦΘΕͨޙͰ return ͞ΕΔͱ྆ऀͱ΋ 2 Λදࣔ͢Δɻ → σʔλڝ߹

ैདྷͷղܾ๏: ϩοΫ class Counter { var count: Int = 0 func increment() -> Int { lock() defer { unlock() } count += 1 return count } } ϩοΫΛ࢖͏ͱεϨουΛϒϩοΫͯ͠͠·͏ύϑΥʔϚϯε্ ͷෆརӹʹՃ͑ͯɺσουϩοΫͷݪҼͱͳΔڪΕ͕͋Δɻ

ैདྷͷղܾ๏: γϦΞϧΩϡʔ ΦϖϨʔγϣϯΛγϦΞϧΩϡʔʹೖΕͯɺΩϡʔ͕Ұͭͣͭॱ ൪ʹऔΓग़ͯ͠ॲཧΛ͢Δɻσʔλڝ߹΋σουϩοΫ΋ى͜Β ͳ͍ɻ

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ैདྷͷղܾ๏: γϦΞϧΩϡʔ class Counter { let queue = ... var count: Int = 0 func increment(completion: (Int) -> Void) { queue.async { count += 1 completion(count) } } } ࣮૷͕ෳࡶͩͬͨΓɺΩϡʔΛ࢖͏ͷΛ๨ΕͨΓ͕ͪ͠ɻ

// γϦΞϧΩϡʔΛ࢖͏ݱ࣮ͷίʔυ͸ΑΓෳࡶ let queue = DispatchQueue(...) func load(_ url: URL) { queue.sync { // ϝϞϦΩϟογϡΛ୳͢ ... } queue.sync { // σΟεΫΩϟογϡΛ୳͢ ... } queue.async { // ը૾Λμ΢ϯϩʔυ fetch(url) { if { // ੒ޭ: Ωϟογϡʹอଘ // ίʔϧόοΫΛݺͿ ... } else if { // ηογϣϯ੾Ε: queue.async { // ϦϑϨογϡτʔΫϯͰϦτϥΠ } ... } else { // ࣦഊ: ΤϥʔϋϯυϥΛݺͿ ... } } } }

actor ʹΑΔղܾ actor Counter { var count: Int = 0 func increment() -> Int { count += 1 return count } } ΩϡʔʹೖΕΔͷͱಉ͡Α͏ͳ͜ͱΛίϯύΠϥ͕ߦͬͯ͘Ε ΔɻύϑΥʔϚϯε΋ΑΓྑ͍ɻ

actor ͷϝιουΛ֎͔ΒݟΔͱ actor Counter { ... func increment() async -> Int { ... } } actor ֎෦͔Β͸ async ϝιουʹݟ͑Δɻ

actor ͷϝιουΛ֎͔ΒݟΔͱ let counter = Counter() print(await counter.increment())

actor ͷϝιουΛத͔ΒݟΔͱ actor Counter { var count: Int = 0 func countUp(amount: Int) -> Int { count += amount return count } func increment() -> Int { countUp(amount: 1) // ಉظݺͼग़͠ } } ֎͔ΒݟͨΒ async ͚ͩͲɺத͔ΒݟͨΒಉظతɻ

actor • ΦϖϨʔγϣϯΛΩϡʔʹೖΕͯॱ൪ʹߦ͏ͷͰσʔλڝ߹͕ ى͜Βͳ͍ • actor ͕ࣗಈతʹΦϖϨʔγϣϯΛΩϡʔʹೖΕΔͷͰΩϡʔ ʹೖΕ๨Εͳ͍ • ֎෦͔Β͸ async ʹݟ͑ɺϒϩοΩϯά͕ଘࡏ͠ͳ͍ͷͰσο υϩοΫ͕ى͜Βͳ͍

͜Ε͚ͩͰ͸σʔλڝ߹Λ׬શʹ͸๷͛ͳ͍

actor ʹ౉ͨ͠ΠϯελϯεΛ֎෦͔Βมߋ actor Foo { func method(x: X) { ... } } let foo = Foo() let x = X() foo.method(x: x) x.value += 1 // कΒΕ͍ͯͳ͍

actor ʹ౉ͨ͠ΠϯελϯεΛ֎෦͔Βมߋ actor Foo { func method(x: X) { ... } } let foo = Foo() let x = X() foo.method(x: x) // ⛔ ίϯύΠϧΤϥʔ x.value += 1 ϛϡʔλϒϧΫϥεͷΠϯελϯεΛ౉͢ͱίϯύΠϧΤϥʔɻ ஋ܕ΍ΠϛϡʔλϒϧΫϥεͷΠϯελϯε͸౉ͤΔɻ

actor ͔Βड͚औͬͨΠϯελϯεΛ֎෦͔Βมߋ actor Foo { let x = X() func method() -> X { return x } } let foo = Foo() let x = await foo.baz() // ⛔ ίϯύΠϧΤϥʔ x.count += 1 ϛϡʔλϒϧΫϥεͷΠϯελϯεΛฦ͢ͱίϯύΠϧΤϥʔɻ ஋ܕ΍ΠϛϡʔλϒϧΫϥεͷΠϯελϯε͸औΓग़ͤΔɻ

ͦͷଞʹɺσουϩοΫΛ׬શʹ๷͙ͨΊʹ ͸ actor ͷ Reentrancy ͕ɾɾɾ ͕࣌ؒ଍Γͳ͍ͷͰৄࡉ͸ Proposal SE-0304 Λޚཡ͍ͩ͘͞ɻ SE-0304 Structured concurrency h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0304-structured- concurrency.md

·ͱΊ ! async/await " Structured Concurrency # actor ͜ΕΒͷ࢓૊ΈΛ༻͍ͯɺฒߦॲཧͰσʔλڝ߹ͱσουϩοΫ ͕ى͜Βͳ͍͜ͱΛίϯύΠϥ͕อূɻ

ࢀߟจݙ 10254 Swi$ concurrency: Behind the scenes h(ps:/ /developer.apple.com/videos/play/wwdc2021/10254/ 10134 Explore structured concurrency in Swi3 h'ps:/ /developer.apple.com/videos/play/wwdc2021/10134/ 10133 Protect mutable state with Swi2 actors h&ps:/ /developer.apple.com/videos/play/wwdc2021/10133/ 10132 Meet async/await in Swi. h'ps:/ /developer.apple.com/videos/play/wwdc2021/10132/ WWDC 2021 Sessions SE-0317 async let bindings h*ps:/ /github.com/apple/swi<-evolu>on/blob/main/proposals/0317-async-let.md SE-0316 Global actors h*ps:/ /github.com/apple/swi<-evolu>on/blob/main/proposals/0316-global-actors.md SE-0306 Actors h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0306-actors.md SE-0304 Structured concurrency h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0304-structured- concurrency.md SE-0302 Sendable and @Sendable closures h)ps:/ /github.com/apple/swi;-evolu=on/blob/main/proposals/0302- concurrent-value-and-concurrent-closures.md SE-0296 Async/await h*ps:/ /github.com/apple/swi<-evolu>on/blob/main/proposals/0296-async-await.md Swi$ Evolu+on Proposals