20180410_iOSLT_SwiftとProtocol-OrientedProgramming

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SwiftͱProtocol-Oriented Programming 2018.4.10 Shota Nakagami / @shtnkgm

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ຊ೔ͷΰʔϧ ϓϩτίϧࢦ޲Λ஌ͬͯɺ΋ͬͱSwiftyͳΤϯδχΞʹ

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"Swift is a protocol-oriented language. " — David Abrahams @WWDC2015

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Google Trendsʮprotocol-oriented programmingʯ

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ϓϩτίϧΦϦΤϯςουͬͯͳΜͩΖ͏ʁ !

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Protocol-Oriented Programming: POP • ༁͢ͱϓϩτίϧࢦ޲ϓϩάϥϛϯά • ϓϩτίϧࢦ޲ϓϩάϥϛϯά͸ϓϩάϥϛϯάύϥμΠϜͷ Ұͭ

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ϓϩάϥϛϯάύϥμΠϜͬͯͳΜͩΖ͏ʁ !

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Programming Paradigm • ϓϩάϥϛϯάΛ͢Δͱ͖ͷߟ͑ํɺํ๏࿦ͷ͜ͱ • ҰͭͷݴޠͰෳ਺ͷύϥμΠϜʹ෼ྨ͞ΕΔ͜ͱ΋͋Δ ʢ= ϚϧνύϥμΠϜʣ

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ϓϩάϥϛϯάύϥμΠϜͷҰྫ ϓϩάϥϛϯάύϥμΠϜ ֓ཁ खଓ͖ܕʢProceduralʣ ঢ়ଶΛ࣋ͪɺҰ࿈ͷॲཧΛؔ਺ʹ·ͱΊΔ ΦϒδΣΫτࢦ޲ʢObject-Orientedʣ σʔλ΍ৼΔ෣͍ΛΦϒδΣΫτʹ࣋ͨͤΔ ؔ਺ܕʢFunctionalʣ ঢ়ଶ΍෭࡞༻Λ࣋ͨͳ͍ؔ਺Λ૊Έ߹ΘͤΔ ϦΞΫςΟϒʢReactiveʣ σʔλͷྲྀΕʢdata ﬂowʣͱσʔλͷมԽͷ ఻೻ʹண໨ δΣωϦοΫʢGenericʣ σʔλܗࣜʹґଘ͠ͳ͍ ΞεϖΫτࢦ޲ʢAspect-Orientedʣ ԣஅతؔ৺ࣄͷ෼཭ʹண໨

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iOSΞϓϦ։ൃ͸ϚϧνύϥμΠϜ • Objective-CɾɾɾΦϒδΣΫτࢦ޲ • Swiftɾɾɾϓϩτίϧࢦ޲ ʢΦϒδΣΫτࢦ޲&ؔ਺ܕ&δΣωϦοΫʣ • ಛʹɺUIKit͸ΦϒδΣΫτࢦ޲ͱͷؔΘΓ͕ڧ͍

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ΦϒδΣΫτࢦ޲ͬͯͳΜ͚ͩͬʁ

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ΦϒδΣΫτࢦ޲ͷ͓͞Β͍

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Object-Oriented Programming: OOP • σʔλ΍ϝιουΛ࣋ͬͨΦϒδΣΫτΛͭͬͯͦ͘ͷ૬ޓ࡞ ༻ͰγεςϜΛܗ࡞Δ • ΦϒδΣΫτࢦ޲ͷࡾݪଇ • ϙϦϞʔϑΟζϜʢଟଶੑʣ • ΧϓηϧԽʢӅṭʣ • ܧঝ

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UIKitͷΫϥε֊૚

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ΦϒδΣΫτࢦ޲ͱϓϩτίϧࢦ޲

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Swift Standard Framework͸΄΅ߏ଄ମͰߏ੒ ओͳߏ੒ཁૉ ΦϒδΣΫτࢦ޲ ϓϩτίϧࢦ޲ ܕ ࢀরܕʢClassʣ ஋ܕʢStruct/Enumʣ ந৅Խ Superclass Protocol →Obective-C࣌୅ͷΫϥεͷར༻͔Βߏ଄ମͷར༻͕த৺ʹ

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ΦϒδΣΫτࢦ޲Ͱʮಈ෺ʯΛσβΠϯͯ͠ΈΔ

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͍ΖΜͳಈ෺ΫϥεΛͭ͘Γ·͢

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class Fish { } class Cat { } class Dog { } class Bird { }

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Ͳͷಈ෺΋͝͸ΜΛ৯΂Δ →ॲཧΛڞ௨Խ͍ͨ͠

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class Fish { func eat() { /* something */ } } class Cat { func eat() { /* something */ } } class Dog { func eat() { /* something */ } } class Bird { func eat() { /* something */ } }

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਌Ϋϥεʹڞ௨ॲཧΛ࣮૷ͯ͠ܧঝ

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class Animal { func eat() { /* something */ } } class Fish: Animal { } class Cat: Animal { } class Dog: Animal { } class Bird: Animal { }

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Ҡಈํ๏΋·ͱΊΒΕͦ͏ʁ

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਌Ϋϥεʹ࣮૷ʁ

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class Animal { func eat() { /* something */ } func swim() { /* something */ } func run() { /* something */ } func fly() { /* something */ } } class Dog: Animal { } let dog = Dog() dog.fly()

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class Animal { func eat() { /* something */ } func swim() { /* something */ } func run() { /* something */ } func fly() { /* something */ } } class Dog: Animal { } let dog = Dog() dog.fly()

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ۭඈͿ͍͵͕ൃੜʢόάʣ

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Ҡಈํ๏ʹ͍ͭͯͷந৅֓೦Λ࣮૷

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ΑΓ҆શͳϓϩάϥϜʹ class Animal { func eat() { /* something */ } } class RunAnimal: Animal { func run() { /* something */ } } class Dog: RunAnimal { } let dog = Dog() dog.run() // OK dog.fly() // ίϯύΠϧΤϥʔ

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ʊਓਓਓਓਓਓਓਓਓʊ ʼɹಥવͷ࢓༷มߋɹʻ ʉY^Y^Y^Y^Y^Y^Y^Yʉ

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ӭ͛ͯ૸ΕΔΧΤϧ͸ʁ

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Ϋϥε͸ଟॏܧঝΛαϙʔτ͍ͯ͠ͳ͍ // error: multiple inheritance from classes 'SwimAnimal' and 'RunAnimal' class Frog: SwimAnimal, RunAnimal { }

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Ϋϥεͷܧঝʹؔ͢Δ໰୊ᶃ • ୯Ұʢ୯७ʣܧঝ͔͠Ͱ͖ͳ͍ͷͰɺΫϥεઃܭ͕೉͍͠ ɹˠ਌Ϋϥε͕ංେԽɺڽू౓͕௿͘ͳΓ͕ͪʢͪ͝Ό·ͥʣ

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Ϋϥεͷܧঝʹؔ͢Δ໰୊ᶄ • ਌Ϋϥεͷมߋ͕શͯͷܧঝઌΫϥεʹ೾ٴ͢Δ ɹ →όάͷݪҼɺ਌Ϋϥε͸มߋ͠ʹ͍͘

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Ϋϥεͷܧঝʹؔ͢Δ໰୊ᶅ • ந৅֓೦΋ΠϯελϯεԽͰ͖ͯ͠·͏ →όάͷݪҼ // ۩৅ΫϥεͷΠϯελϯεԽ let dog = Dog() let frog = Frog() // ந৅ΫϥεͷΠϯελϯεԽ let animal = Animal() // ͲΜͳಈ෺ʁ

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Ϋϥεͷܧঝʹؔ͢Δ໰୊ᶆ • ΦʔόʔϥΠυલఏͷϝιου class Animal { func bark() { // ಈ෺ͱ͍͏֓೦͸ͳΜͯ໐͘?? // // } }

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Ϋϥεͷܧঝʹؔ͢Δ໰୊ᶆ • ΦʔόʔϥΠυલఏͷϝιου class Animal { func bark() { // ಈ෺ͱ͍͏֓೦͸ͳΜͯ໐͘?? // ΦʔόʔϥΠυ͞Εͳ͍৔߹͸Ϋϥογϡͤ͞Δ͔... fatalError() } } ܧঝઌͰͷ࣮૷࿙Ε͕͋Δͱόάͷݩʹ

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ϓϩτίϧࢦ޲Ͱʮಈ෺ʯΛσβΠϯͯ͠ΈΔ

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Protocol Conformance ϓϩτίϧ४ڌʢద߹ʣ

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ੑ࣭ΛϓϩτίϧͰදݱͯ͠४ڌ

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protocol Eatable { func eat() } struct Cat: Eatable { // eatϝιουͷ࣮૷͕ڧ੍͞ΕΔ // ίϯύΠϥͰνΣοΫ͞ΕΔͷͰ҆શ func eat() { print("ͺ͘ͺ͘") } }

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Protocol Extension ϓϩτίϧΤΫεςϯγϣϯʢ֦ுʣ

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ϓϩτίϧΤΫεςϯγϣϯͰσϑΥϧτ࣮૷ protocol Eatable { func eat() } extension Eatable { func eat() { print("΋͙΋͙") } } struct Dog: Eatable { } let dog = Dog() dog.eat() // ΋͙΋͙

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Protocol Composition ϓϩτίϧίϯϙδγϣϯʢ߹੒ʣ

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ෳ਺ϓϩτίϧ४ڌͰΧΤϧ໰୊ղফ

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struct Frog: Swimmable, Runnable { } let frog = Frog() frog.swim() frog.run()

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Protocol Inheritance ϓϩτίϧܧঝ

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ϓϩτίϧܧঝ΋Մೳ

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protocol Movable { func move(method: String) } extension Movable { func move(method: String) { print(method + "ਐΈ·͢") } } protocol Swimmable: Movable { func swim() } extension Swimmable { func swim() { move(method: "ӭ͍Ͱ") } } struct Fish: Swimmable { } let fish = Fish() fish.swim() // ӭ͍ͰਐΈ·͢

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͞ΒʹFlyableΛಈ෺Ͱͳ͍ܕͰ४ڌ • e.g. ඈߦػ • ඈͿͱ͍͏ੑ࣭͔Βઃܭ͢Δ͜ͱͰɺಈ෺ʹ΋ґଘ͠ͳ͍ • ॊೈͰ֦ுੑͷ͋ΔϓϩάϥϜʹͳΔ

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ϓϩτίϧ͸஋ܕͰ΋࢖͑Δ • ஋ܕͷStruct΍Enumʹ͸ΫϥεͷΑ͏ͳܧঝػೳ͸ͳ͍͕ɺϓ ϩτίϧʹ͸४ڌͰ͖Δ • ஋ܕ͸ࢀরܕʢΫϥεʣΑΓ΋҆શ • ஋Λڞ༗͠ͳ͍ͷͰҙਤ͠ͳ͍஋ͷมߋ͕ൃੜ͠ͳ͍ • εϨουηʔϑ • ॥؀ࢀর໰୊͕ൃੜ͠ͳ͍

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ϓϩτίϧ͸ܕͱͯ͠ѻ͑Δ • ϙϦϞʔϑΟζϜͰૄ݁߹ʹ ! func feed(eatable: Eatable) • ΠϯελϯεԽෆՄ ! // Error: Protocol type 'Eatable' cannot be instantiated let eatable = Eatable()

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δΣωϦΫεʢ૯শܕʣ΋࢖͑Δ Ϋϥε΍StructͷΑ͏ͳܕύϥϝʔλ͸࢖͑ͳ͍͕ɺ associatedtypeͰ૯শܕΛఆٛͰ͖Δ class Eatable { } struct Eatable { } protocol Eatable { associatedtype FoodType }

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protocol Eatable { associatedtype FoodType func eat(food: FoodType) } struct Bird: Eatable { typealias FoodType = Fish func eat(food: FoodType) { // do something } }

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ϓϩτίϧࢦ޲͍͍Ͷ

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·ͱΊ

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࠷ڧͷϓϩάϥϛϯάύϥμΠϜ͸ͳ͍ • ͲΕ΋໰୊ղܾͷखஈͷҰͭʹ͗͢ͳ͍ • ϓϩτίϧࢦ޲Λ஌Δ͜ͱͰϓϩάϥϛϯάͷ෯͕޿͕Δ • ͍ΖΜͳํ๏࿦Λ஌Γɺదࡐదॴ࢖͑Δͷ͕࠷ڧ

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ΦϒδΣΫτࢦ޲ ϓϩτίϧࢦ޲ σʔλͷ҉໧తڞ༗ ×ʢ͋Γʣ ○ʢͳ͠ʣ ந৅Խ ○ʢSuperclassʣ ○ʢProtocolʣ ίϯϙδγϣϯ ×ʢͰ͖ͳ͍ʣ ○ʢProtocol Compositionʣ ந৅ܕͷΠϯελϯεԽ ×ʢͰ͖Δʣ ○ʢͰ͖ͳ͍ʣ σϑΥϧτ࣮૷ ○ʢSuperclassʣ ○ʢProtocol Extensionʣ ۩৅ܕ΁ͷ࣮૷ͷڧ੍ ×ʢಈతνΣοΫʣ ○ʢ੩తνΣοΫʣ ϙϦϞʔϑΟζϜ ○ʢSuperclassʣ ○ʢProtocolʣ δΣωϦΫε ○ʢܕύϥϝʔλʣ ○ʢassociatedtypeʣ UIKitΦϒδΣΫτͷܧঝ ○ʢͰ͖Δʣ ×ʢͰ͖ͳ͍ʣ ϥΠϑαΠΫϧ؅ཧʢdeinitʣ ○ʢ͋Γʣ ×ʢͳ͠ʣ Ұҙੑͷ͋Δσʔλʢsingletonʣ ○ʢ࡞Γ΍͍͢ʣ ×ʢ࡞Γʹ͍͘ʣ

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ΑΓৄ͘͠ • WWDC2015ηογϣϯಈը Protocol-Oriented Programming in Swift / WWDC2015 • ެࣜϦϑΝϨϯε Protocols / The Swift Programming Language (Swift 4.1) • ॻ੶ Swift 4 Protocol-Oriented Programming - Third Edition

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͓ΘΓ