Types in Swift - Speaker Deck

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ܕ @yashigani Cocoaษڧձؔ੢ #60

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yashigani id:yashigani_w @yashigani Mobile Application Engineer http://yashigani.hatenablog.com Hatena

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https://ﬂic.kr/p/nBzE6V ܕʹϋϚͬͨ͜ͱ͸͋Γ·͔͢ • ίϯύΠϧΤϥʔʹͳΔ΍ͭͰ͠ΐʁ • ܕ੍ͬͯ໿ͳ͚ͩͰͱʹ͔͘अຐ • id࠷ߴ΍Μʂʂʂܕͱ͔͍ΒΜʂʂʂ

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ܕͬͯԿʁ

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ܕ͸ৼΔ෣͍

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ৼΔ෣͍ • ৼΔ෣͍ = σʔλߏ଄ + ॲཧ • Ͳ͏͍͏σʔλ͕Ͳ͏ಈ࡞͢Δ͔༧૝Ͱ͖Δ • ΠϯλʔϑΣʔε͕ݫ֨

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ΞυϨε௕ͷϝλσʔλ • ϝϞϦۭؒʹ͓͚Δม਺ͷҐஔ • ௿ϨΠϠͷॲཧ͕Մೳͳނ • ϓϦϛςΟϒ͗͢Δ

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0CKFDUJWF$

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ৼΔ෣͍ͷϝλσʔλ • isaϙΠϯλ • ม਺͕ৼΔ෣͏΂͖͜ͱΛࣔࠦ(ಈతσΟεύον) • ͨͩ͠ඞͣ͠΋ै͑Δͱ͸ݶΒͳ͍ • ม਺ͷৼΔ෣͍Λଋറ͢Δ΋ͷͰ͸ແ͍

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4XJGU

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ৼΔ෣͍Λ໿ଋ͢Δ΋ͷ • ৼΔ෣͍Λม਺ʹଋറ • ͋Δܕͷม਺͸ͦͷܕͷৼΔ෣͍͔͠͠ͳ͍ • ܕͷ͋Δϓϩάϥϛϯά͕Մೳ

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ͳͥϓϩάϥϜʹ ܕ͕ඞཁͳͷ͔

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ܕ ܕ͕͋Δ͔ΒɺܕഁΓɻ ܕ͕ͳ͚Ε͹୯ͳΔʮܗແ͠ʯ ʕेീ୅໨தଜצࡾ࿠ Վ෣ب໾ऀ

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/4%JDUJPOBSZ

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NSDictionary *user = //... NSString *name = user[@"name"];

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NSDictionary *user = //... NSString *name; if ([user[@"name"] isKindOfClass: [NSString class]]) { //!!!!! name = user[@"name"]; } else { //!!!!! }

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https://ﬂic.kr/p/7BD2UE Too bad ߏ଄͕ෆ໌ͳͷͰσʔλͷଘࡏΛஅఆͰ͖ͳ͍ Կ͕ೖ͍ͬͯΔͷ͔ෆ໌ͳͷͰσʔλܕΛࢦఆ ৼΔ෣͍͕ແ͍

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ܕ͕ແ͍

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.PEFM0CKFDU JO0CKFDUJWF$

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@interface User : NSObject @property (copy) NSString *name; @property NSUInteger age; @property (getter=isPremium) BOOL premium; @end

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User *user = //... UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@" cell"]; cell.textLabel.text = user.name;

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User *user = //... UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@" cell"]; if (user.name != nil) { cell.textLabel.text = user.name; } else { //!!!!! }

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https://ﬂic.kr/p/i74K6M Too bad σʔλͷߏ଄ͱܕ͸දݱͰ͖ͨ ΠϯλʔϑΣʔε͕ෆఆ(nilͷՄೳੑ) ৼΔ෣͍͚͕ͩ͋Δ(ଋറ͕ແ͍)

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ܗແ͠

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.PEFM0CKFDU JO4XJGU

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struct User { let name: String let age: Int let isPremium: Bool }

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let user = //... let cell = tableView.dequeueReusableCellWithId entifier("cell") cell?.titleLabel.text = user.name

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https://ﬂic.kr/p/egaNwP Relaxed ෆ֬ఆͳཁૉ͸ϏδωεϩδοΫʹӅṭ ΞϓϦέʔγϣϯ͸σʔλΛදࣔ͢Δ͚ͩ ৼΔ෣͍Λଋറ͢Δ͜ͱͰ໿ଋ͞Εͨڍಈ

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5IJTJTܕ

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ܕͷ͋ΔϓϩάϥϜ • ৼΔ෣͍͕໌֬Ͱ׬શ • ͕ͨͬͯ͠ෆඞཁͳ৺഑͕͍Βͳ͍ • ϏδωεϩδοΫͱΞϓϦέʔγϣϯͷ෼཭ • ΠϯλʔϑΣʔεͷΈʹґଘ࣮ͨ͠૷

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0OFNPSFUIJOH

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func parse(JSON: AnyObject?) -> (User?, NSError?) let JSON: AnyObject? = //... let (user, error) = parse(JSON) if let e = error { //... return } if let u = user { //... } else { // maybe user is nil... }

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https://ﬂic.kr/p/DC3Q Too bad user΋error΋nilͷͱ͖͸Ͳ͏͍͏Τϥʔʁ ΋ͬͱ΋ͬͱstrictʹදݱ͍ͨ͠ (User?, NSError?)͸ૉ๿͗͢Δ

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ܕΛഁΔ ܕʹΑΔܕͷந৅Խ

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3FTVMU5

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enum Result { case Success(T) case Failure(NSError) init(_ value: T) { self = .Success(value) } init(_ error: NSError) { self = .Failure(error) } }

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ܕഁΓٕͦͷ ʙHFOFSJDTʙ

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enum Result { case Success(T) case Failure(NSError) init(_ value: T) { self = .Success(value) } init(_ error: NSError) { self = .Failure(error) } } generics

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ҦΘ͹ϫΠϧυΧʔυܕ • ͱΓ͋͑ͣ͸ͳΜͰ΋ೖΕΒΕΔܕ • ಉ͡ϥϕϧͷ΋ͷ͸ಉ͡ܕ • ΠϯλʔϑΣʔεΛܾΊͨͱ͖ʹܕ͕ܾ·Δ • func parse(_:AnyObject) -> Result • Any/AnyObjectͱҧͬͯղ͘ͱ͖ʹ౎౓ͳʹ͔  ͔֬ΊΔඞཁ͕ແ͍

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ܕഁΓٕͦͷ ʙFOVNʙ

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enum Result { case Success(T) case Failure(NSError) init(_ value: T) { self = .Success(value) } init(_ error: NSError) { self = .Failure(error) } } enum

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ෳ਺ͷঢ়ଶΛऔΓ͏Δ • Aঢ়ଶͳΒaΛ࣋ͬͯΔ͚ͲɼBঢ়ଶͰ͸࣋ͬͯͳ͍ • ͱΓ͋͑ͣAnyObjectʹͿͪࠐ·ͳ͍͍ͯ͘ • ͲΕ͔ͻͱͭͷঢ়ଶ͔͠औΓಘͳ͍ • A͔ͭBͳঢ়ଶ͸ଘࡏ͠ͳ͍

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ͭ·ΓResultͱ͸ • ੒ޭ͔ࣦഊ͔ΛऔΓ͏Δ஋ • ੒ޭͨ͠ΒT͕ɼࣦഊͨ͠ΒNSError͕ಘΒΕΔ • ୯७ʹOptional஋Λฒ΂Δͷʹൺ΂ͯѻ͍΍͍͢ • ྆ํ஋͕͋Δ྆ํແ͍ͳΜͯ͜ͱ͸͋Γ͑ͳ͍

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func parse(JSON: AnyObject?) -> Result let JSON: AnyObject? = // ... let result = parse(JSON) switch result { case .Success(let user): // ... case .Failure(let error): // ... }

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+VTUB&JUIFS

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0QUJPOBM

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Optional΋ಉྨ • Optional͸ͻͱͭͷgenericܕΛऔΔenum • enum Optional • ͳʹ͔ͷ஋͕͋Δ/ͳ͍ͷ2छྨͷঢ়ଶΛऔΓ͏Δ • SomeͩͬͨΒTΛ࣋ͬͯΔ • NoneͩͬͨΒnilΛ࣋ͬͯΔ