ϝϧΧϦ ΞοςΛࢧ͑Δ ΦʔτϚτϯ Vu Nhat Minh / @orakaro Souzoh iOS Talk

Mercari Atte Scala / Swift Engineer / @orakaro

Ξος͕औΓ૊ΜͰ͍Δ͜ͱ • ϑϧRxSwift • Driverʹੵۃతʹஔ͖׵͑Δ • ViewModelͷΠϯϓοτɺΞ΢τϓοτԽ • ܧঝΑΓίϯϙδγϣϯ • ΦʔτϚτϯ

εςʔτϚγϯͷ͓͞Β͍ • ༗ݶΦʔτϚτϯ • ભҠؔ਺ͷΈ (s, a) -> s • Mealy Machine • ભҠؔ਺ (s, a) -> s • ग़ྗؔ਺ (s, a) -> b • Moore Machine • ભҠؔ਺ (s, a) -> s • ग़ྗؔ਺ s -> b

༗ݶΦʔτϚτϯ • ༗ݶΦʔτϚτϯ • ભҠؔ਺ͷΈ (s, a) -> s • Mealy Machine • ભҠؔ਺ (s, a) -> s • ग़ྗؔ਺ (s, a) -> b • Moore Machine • ભҠؔ਺ (s, a) -> s • ग़ྗؔ਺ s -> b ঢ়ଶΛ؅ཧ͍ͨ࣌͠ʹ׆༻͢΂͖

Binary Gap A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ends in the binary representation of N. Ex: 9 = 1001 → 2

A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ends in the binary representation of N. Ex: 9 = 1001 → 2 Started Zero One Binary Gap

Visual Format Language class func constraints(withVisualFormat format: String, options opts: NSLayoutFormatOptions = [], metrics: [String : Any]?, views: [String : Any]) -> [NSLayoutConstraint] "H:|-15-[iconImageView(30)]-[appNameLabel]-[skipButton]-15-|"

Visual Format Language class func constraints(withVisualFormat format: String, options opts: NSLayoutFormatOptions = [], metrics: [String : Any]?, views: [String : Any]) -> [NSLayoutConstraint] "H:|-15-[iconImageView(30)]-[appNameLabel]-[skipButton]-15-|" Direction Start Line Number Label [ ] ( ) End

݈શͳίʔυϕʔεͷͨΊʹ ڊେif elseΛʢͰ͖Ε͹ʣॻ͔ͳ͍ άϩʔόϧม਺ΛʢͰ͖Ε͹ʣ࢖Θͳ͍ ؔ਺ ΛʢͰ͖Δ͚ͩʣ७ਮؔ਺ʹ͍ͨ͠

ձһొ࿥ϑϩʔ ʁ ʁ ʁ ʁ ʁ

ձһొ࿥ϑϩʔ Emailొ࿥͍ͤͨ͞ Facebookೝূ͍ͤͨ͞ ϝϧΧϦొ࿥ࡁΈͳΒϫϯΫϦοΫ ύεϫʔυ࠶ઃఆ ϩάΠϯ͍ͤͨ͞

ձһొ࿥ϑϩʔ

ొ࿥ঢ়ଶ൑ఆ

Facebookೝূ

ϝʔϧϩάΠϯ

ձһొ࿥ʢΠϝʔδʣ Root Register Root Profile Register Start With Mercari AtteLogin Facebook Email Login Register With Mercari Confirm SMS Home PassCode Email SignUp Reset Password

Root Register Root Profile Register Start With Mercari AtteLogin Facebook Email Login Register With Mercari Confirm SMS Home PassCode Email SignUp Reset Password

ભҠϩδοΫ͸υϝΠϯ஌ࣝ Ϟσϧ૚Ͱ؅ཧ͢΂͖ MVC / MVP / MVVM

΋͸΍֤ը໘͕ εςʔτΛදݱ͍ͯ͠Δͷ͡Ό

ΠϕϯτʹΑͬͯભҠ Root Register Root Atte Login Start With Mercari Atte Resource Mercari Resource

RegistrationStateViewController protocol RegistrationStateViewController { var state: RegistrationState { get } func nextViewController(event: RegistrationEvent) -> UIViewController? } extension RegistrationStateViewController { func nextViewController(event: RegistrationEvent) -> UIViewController? { let machine = AutomatonManager.registrationMachine guard let state = machine.transition(from: state, by: event) else { return nil } switch state { //... } } ΦʔτϚτϯ

TransitionΛఆٛ struct Transition { let from: S let to: S let by: E } from to by State State Event

State MachineΛ࣮૷ class Automaton { var routes: [S: [E: S]] = [:] init(initialState: S, transitions: [Transition]) { for t in transitions { addRoute(t) } } private func addRoute(_ t: Transition) { var dict = routes[t.from] ?? [:] dict[t.by] = t.to routes[t.from] = dict } func transition(from: S, by: E) -> S? { guard let next = routes[from].flatMap({ $0[by] }) else { return nil } return next } }

State MachineΛ࣮૷ class Automaton { var routes: [S: [E: S]] = [:] init(initialState: S, transitions: [Transition]) { for t in transitions { addRoute(t) } } private func addRoute(_ t: Transition) { var dict = routes[t.from] ?? [:] dict[t.by] = t.to routes[t.from] = dict } func transition(from: S, by: E) -> S? { guard let next = routes[from].flatMap({ $0[by] }) else { return nil } return next } } ࣙॻܕΛ࢖ͬͯભҠΛ؅ཧ͢Δ

εςʔτͱΠϕϯτΛఆٛ enum RegistrationState { case root case registerRoot case profileRegister case startWithMercari case emailLogin case atteLogin case home } enum RegistrationEvent: Hashable { case showRegisterRoot(loginMode: RootViewController.LoginMode?) case registerWithFacebook(profile: FacebookProfile?) case startWithMercari(resource: MercariIdResource?, tokenPair: TokenPair?, showsCloseButton: Bool) case loginWithEmail(showsCancelButton: Bool) case loginWithAtte(resource: MercariIdResource?, tokenPair: TokenPair?) case loginAndShowHome(tokenPair: TokenPair?, userId: Int64, hasMercariItem: Bool) }

ભҠάϥϑΛఆٛ let registrationGraph: [Transition] = [ Transition(from: .root, to: .registerRoot, by: DefaultEvent.showRegisterRoot), Transition(from: .registerRoot, to: .profileRegister, by: DefaultEvent.registerWithFacebook), Transition(from: .registerRoot, to: .startWithMercari, by: DefaultEvent.startWithMercari), Transition(from: .registerRoot, to: .emailLogin, by: DefaultEvent.loginWithEmail), Transition(from: .registerRoot, to: .atteLogin, by: DefaultEvent.loginWithAtte), Transition(from: .registerRoot, to: .home, by: DefaultEvent.loginAndShowHome), ] let registrationMachine = Automaton( initialState: .root, transitions: registrationGraph )

ભҠϩδοΫ͚ͩςετͰ͖Δ describe("ΞϓϦىಈ࣌τʔΫϯ͕ଘࡏ͠ͳ͍") { it("ϝʔϧͰ৽نొ࿥͕Ͱ͖Δ") { self.tryRoute(events: [ DefaultEvent.showRegisterRoot, DefaultEvent.registerWithEmail, DefaultEvent.showProfileRegister, DefaultEvent.confirmSMS, DefaultEvent.loginAndShowHome ]) XCTAssert(self.currentState == .home) } } //... private func tryRoute(events: [RegistrationEvent]) { for event in events { self.currentState.map { state in self.currentState = self.machine.transition(from: state, by: event) } } }

No content

·ͩ໰୊͕͋Δ

RegistrationStateViewController protocol RegistrationStateViewController { var state: RegistrationState { get } func nextViewController(event: RegistrationEvent) -> UIViewController? } extension RegistrationStateViewController { func nextViewController(event: RegistrationEvent) -> UIViewController? { let machine = AutomatonManager.registrationMachine guard let state = machine.transition(from: state, by: event) else { return nil } switch state { //... } } ͜͜ͰViewControllerΛੜ੒͢Δͷʁ

RegistrationStateViewController switch state { case .root: return RootViewController.make(withDependency: ()) case .registerRoot: return RegisterRootViewController.make(withDependency: ()) case .profileRegister : switch event { case .registerWithFacebook(.some(let profile)): return ProfileRegisterViewController.make(withDependency: .init(facebookProfile: profile)) default: return nil } case .startWithMercari: switch event { case .startWithMercari(.some(let resource), .some(let token)): return StartWithMercariViewController.make(withDependency: .init(resource: resource, token: token)) default: return nil } case .emailLogin: return EmailLoginViewController.make(withDependency: ()) case .atteLogin: switch event { case .loginWithAtte(.some(let resource), .some(let token)): return AtteLoginViewController.make(withDependency: .init(resource: resource, token: token)) default: return nil } case .home: switch event { case .loginAndShowHome(.some(let token), let userId): return HomeViewController.make(withDependency: .init(token: token, userId: userId)) default: return nil } default: return nil } ڊେ if elseͱେͯ͠มΘΜͳ͍…

ભҠάϥϑΛఆٛ let registrationGraph: [Transition] = [ Transition(from: .root, to: .registerRoot, by: DefaultEvent.showRegisterRoot), Transition(from: .registerRoot, to: .profileRegister, by: DefaultEvent.registerWithFacebook), Transition(from: .registerRoot, to: .startWithMercari, by: DefaultEvent.startWithMercari), Transition(from: .registerRoot, to: .emailLogin, by: DefaultEvent.loginWithEmail), Transition(from: .registerRoot, to: .atteLogin, by: DefaultEvent.loginWithAtte), Transition(from: .registerRoot, to: .home, by: DefaultEvent.loginAndShowHome), ] let registrationMachine = Automaton( initialState: .root, transitions: registrationGraph ) DefaultEvent !?

DefaultEvent ͬͯԿʁ • Swift 3 ͷassociated value enumʹ͸σϑΥϧτ஋ઃఆͰ͖ͳ͍ • Acceptedͷεςʔλε͕ͩSwift4ʹೖ͍ͬͯͳ͍ Proposal: SE-0155 struct DefaultEvent { static let showRegisterRoot: RegistrationEvent = .showRegisterRoot() static let registerWithFacebook: RegistrationEvent = .registerWithFacebook(profile: nil) static let startWithMercari: RegistrationEvent = .startWithMercari(resource: nil, token: nil) static let loginWithEmail: RegistrationEvent = .loginWithEmail() static let loginWithAtte: RegistrationEvent = .loginWithAtte(resource: nil, token: nil) static let loginAndShowHome: RegistrationEvent = .loginAndShowHome(token: nil, userId: 0) }

enumͷassociated value͕optionalܕ enum RegistrationEvent: Hashable { case showRegisterRoot(loginMode: RootViewController.LoginMode?) case registerWithFacebook(profile: FacebookProfile?) case startWithMercari(resource: MercariIdResource?, tokenPair: TokenPair?, showsCloseButton: Bool) case loginWithEmail(showsCancelButton: Bool) case loginWithAtte(resource: MercariIdResource?, tokenPair: TokenPair?) case loginAndShowHome(tokenPair: TokenPair?, userId: Int64, hasMercariItem: Bool) } Optional

ΦʔτϚτϯ + FP

ભҠؔ਺ (aka Reducer) • ༗ݶΦʔτϚτϯ • ભҠؔ਺ͷΈ (s, a) -> s • Mealy Machine • ભҠؔ਺ (s, a) -> s • ग़ྗؔ਺ (s, a) -> b • Moore Machine • ભҠؔ਺ (s, a) -> s • ग़ྗؔ਺ s -> b

ભҠؔ਺ (s, a) -> s ग़ྗؔ਺ (s, a) -> b Mealy Machine / Moore Machine ભҠؔ਺ (s, a) -> (s, b) ભҠؔ਺ (s, a) -> s ग़ྗؔ਺ s -> b ભҠؔ਺ s -> (a -> s, b)

ભҠؔ਺ (s, a) -> s ग़ྗؔ਺ (s, a) -> b Mealy Machine vs Elm ભҠؔ਺ (s, a) -> (s, b) Elm Architecture fun update(state: State, action: Action): Pair

ભҠؔ਺ (s, a) -> s ग़ྗؔ਺ (s, a) -> b Mealy Machine ભҠؔ਺ (s, a) -> (s, b) ભҠؔ਺ a -> s -> (s, b)

ભҠؔ਺ (s, a) -> s ग़ྗؔ਺ (s, a) -> b Mealy Machine ભҠؔ਺ (s, a) -> (s, b) ભҠؔ਺ a -> s -> (s, b) Stateful Computation !!

ঢ়ଶ෇͖ͷܭࢉʢStateful Computationʣ ঢ়ଶ෇͖ͷܭࢉͱ͸ɺ͋Δঢ়ଶΛऔͬͯɺߋ৽͞Εͨঢ়ଶͱҰॹʹܭࢉ݁ՌΛ ฦؔ͢਺ͱͯ͠දݱͰ͖Δɿ s -> (s, a) class State { private let run: (S) -> (S, A) init(f: @escaping (S) -> (S, A)) { self.run = f } func run(s: S) -> (S, A) { return self.run(s) } }

εςʔτϞφυ ঢ়ଶ෇͖ͷܭࢉͱ͸ɺ͋Δঢ়ଶΛऔͬͯɺߋ৽͞Εͨঢ়ଶͱҰॹʹܭࢉ݁ՌΛ ฦؔ͢਺ͱͯ͠දݱͰ͖Δɿ s -> (s, a) extension State { func map(g: @escaping (A) -> B) -> State { return State { s in let (s1, val) = self.run(s: s) return (s1, g(val)) } } func flatMap(g: @escaping (A) -> State) -> State { return State { s in let (s1, val) = self.run(s: s) return g(val).run(s: s1) } } }

Ϟφυ = flatmappable ܕ Image credit: Functors, Applicatives, And Monads In Pictures

Swift ͷϞφυ Maybe Monad Either Monad Reader Monad Observable Monad State Monad I/O Monad … Swift Optional antitypical/Result Statically typed Dependency Injection Signal / Observable Mealy Machine

ભҠؔ਺ (s, a) -> s ग़ྗؔ਺ (s, a) -> b Mealy Machine ભҠؔ਺ (s, a) -> (s, b) ભҠؔ਺ a -> s -> (s, b) ભҠؔ਺ a -> State[s, b] εςʔτϞφυ

MonadicAutomaton class MonadicAutomaton { typealias T = (A) -> State private var f : T init(f: @escaping T) { self.f = f } func transition(from: S, by: A) -> (S, B) { return f(by).run(s: from) } } ɹભҠؔ਺ A -> State[S, B] A:ΠϯϓοτܕɺB: Ξ΢τϓοτܕ A = ΠϕϯτenumɺB = UIViewController

εςʔτͱΠϕϯτΛఆٛ enum RState { case any case root case registerRoot case profileRegister case startWithMercari case emailLogin case atteLogin case home } enum REvent { case showRegisterRoot case registerWithFacebook(profile: FacebookProfile) case startWithMercari(resource: MercariIdResource, token: String) case loginWithEmail case loginWithAtte(resource: MercariIdResource, token: String) case loginAndShowHome(token: String, userId: Int64) } OptionalͰ͸ͳ͍ʂʂ

ભҠάϥϑΛఆٛ let transitionFunc: (REvent) -> State = { event in switch event { case .registerWithFacebook(let profile): let vc = ProfileRegisterViewController.make(withDependency: .init(facebookProfile: profile)) return State { s in let s1: RState = s == .registerRoot ? .profileRegister : .any return (s1, vc) //... } } let registrationMachine = MonadicAutomaton(f : transitionFunc) A S B A S B

ΦʔτϚτϯ + FRP

ΦʔτϚτϯ + FRP • ը໘಺ͷUIมԽ΋εςʔτʹදݱ͢Δ • ΠϕϯτΛετϦʔϜʹද͢ • ReactiveSwift • inamiy/ReactiveAutomaton • RxSwift • kzaher/RxFeedback

·ͱΊ • ΦʔτϚτϯͷԠ༻ • ༗ݶΦʔτϚτϯ • Mealy Machine • Moore Machine • ঢ়ଶ؅ཧʹ༏ΕΔ • ؆୯ͳભҠॲཧͳΒFSM • Mealy Machine = State Monad

https://github.com/orakaro/MonadicMealyMachine Twitter / Github: @orakaro Q&A