Swift & Kotlin 2017/9/16 ezura

ezura (@eduraaa) • iOS engineer @ LINE
 • like: programming • mock mock radio • ΪϦγϟ఩ֶ / Swift • Blending Kotlin's culture into Swift • ఈ͔ΒֶͿ Swift • …

official on Android

Kotlin

Kotlin OOP extension interface
 default implementati on generics delegation null safety tailrec static
 type Java GC sealed class variance
 declaration object JS companion 
 object if, when expression Type inference (Corout ines) inline annotation FP

• Started in 2010 • Object-oriented programming • Support functional programming • Static typing • Type inference • Null safety • Generic programming

Kotlin’s background

started in 2010 first official 1.0 release in 2016 Let's make a new language
 based on the knowledge 
 that has developed IDEs

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } }

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } } Object-oriented programming

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } } Support functional programming

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } } Static typing

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } } Type inference

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } } Generic programming

class Class: Super() { var property = "" fun method() { var nullable: String? = null if (nullable != null) { nullable.length } val list = listOf(1, 2, 3) list.forEach { print(it) } } } Null safety

• Started in 2010 • Object-oriented programming • Support functional programming • Static typing • Type inference • Null safety • Generic programming

• Started in 2010 • Object-oriented programming • Support functional programming • Static typing • Type inference • Null safety • Generic programming

Swift ͱ Kotlin ͸ࣅ͍ͯΔʁʁ

Swift ͱ Kotlin ͸ࣅ͍ͯΔʁʁ

Swift ͱ Kotlin ͸ࣅ͍ͯΔʁʁ ❌ runtime environment ❌ memory management ❌ background ❌ calling Java/Objective-C ❌ Culture ❌ features

Swift ͱ Kotlin ͸ࣅ͍ͯΔʁʁ Is the learning cost low?

Swift ͱ Kotlin ͸ࣅ͍ͯΔʁʁ ෦෼΋͋Δ Is the learning cost low?

Swift ͱ Kotlin ͸ࣅ͍ͯΔʁʁ ෦෼΋͋Δ Is the learning cost low?

Kotlin ֶश
 Swift ஌ࣝͰϒʔετՄೳ

Index • What is Kotlin • Is Kotlin like Swift? • some keyword • some features • Traps

Index • What is Kotlin • Is Kotlin like Swift? • some keyword • some features • Traps

Syntax Swift Kotlin var, let func f(arg: Any) -> Any class AnyType { … } var obj = Obj() obj.method(arg: v) var, val fun f(arg: Any): Any class AnyType { … } var obj = Obj() obj.method(v) see also: http://nilhcem.com/swift-is-like-kotlin/

Support functional programming Swift Kotlin val f = { x: Int -> /* … */ } obj.map { /* … */ } let f = { Int -> String in /* … */ } obj.map { /* … */ }

Support functional programming Swift Kotlin val f = { x: Int -> /* … */ } obj.map { /* … */ } let f = { Int -> String in /* … */ } obj.map { /* … */ } constant constant

Support functional programming Swift Kotlin val f = { x: Int -> /* … */ } obj.map { /* … */ } let f = { Int -> String in /* … */ } obj.map { /* … */ } first class function first class function

Support functional programming Swift Kotlin val f = { x: Int -> /* … */ } obj.map { /* … */ } let f = { Int -> String in /* … */ } obj.map { /* … */ } higher-order function higher-order function

Null safety Swift Kotlin let i: Int? i?.description if let i = i { i.description } val i: Int? i?.toString() if (i != null) { i.toString() }

Null safety Swift Kotlin let i: Int? i?.description if let i = i { i.description } val i: Int? i?.toString() if (i != null) { i.toString() }

extension Swift Kotlin extension String { func f() {} var v: String { return "" } } let string = "" string.f() string.v fun String.f() = {} val String.v: String get() = ""
 val string = "" string.f() string.v

default implementation 
 for protocol/interface Swift Kotlin protocol P { func f() } extension P { func f() { /* do something */ } } interface I { fun f() { /* do something */ } }

• Started in 2010 • Object-oriented programming • Support functional programming • Static typing • Type inference • Null safety • Generic programming • Some syntax • Extension • Default implementation

Kotlin OOP extension interface
 default implementati on generics delegation null safety tailrec static
 type Java GC sealed class variance
 declaration object JS companion 
 object if, when expression Type inference (Corout ines) inline annotation FP

Kotlin OOP extension interface
 default implementati on generics delegation null safety tailrec static
 type Java GC sealed class variance
 declaration object JS companion 
 object if, when expression Type inference (Corout ines) inline annotation FP

Trap

extension Swift Kotlin extension String { func f() {} var v: String { return "" } } 
 fun String.f() = {} val String.v: String get() = “"

extension Type Type function property function property Swift Kotlin

extension Type Type function property function property Swift Kotlin

extension function Util class instance static Result method(Some target) Some
 Type Java

extension Util.method(instance) Java function Util class instance Some
 Type static Result method(Some target)

extension Collections.max(list) Java function Util class instance Some
 Type static Result method(Some target)

extension max(list) Java function Util class instance Some
 Type static Result method(Some target)

extension max(list) Java function Util class instance Some
 Type list.max() want to … static Result method(Some target)

extension Some
 Type function property Kotlin Util.extensionMethod(instance)

extension Some
 Type function property Kotlin obj.extensionMethod()

extension Type Type function property function property Swift Kotlin extend type by
 functions/properties add
 functions/properties

extension Type Type function property function property Swift Kotlin protocol interface extension String: MyProtocol { /* ... */ } -

extension Type Type function property function property Swift Kotlin extend type by
 functions/properties add
 functions/properties

default implementation 
 for protocol/interface Swift Kotlin protocol P { func f() } extension P { func f() { /* do something */ } } interface I { fun f() { /* do something */ } }

default implementation 
 for protocol/interface Swift Kotlin protocol P { func f() } extension P { func f() { /* do something */ } } interface I { fun f() { /* do something */ } } P f() extension P f()

default implementation 
 for protocol/interface Swift Kotlin protocol P { func f() } extension P { func f() { /* do something */ } } interface I { fun f() } fun I.f() { /* do something */ } P f() extension extension P f()

default implementation 
 for protocol/interface Swift Kotlin protocol P { func f() } extension P { func f() { /* do something */ } } interface I { fun f() } fun I.f() { /* do something */ } class A: I {} // error P f() extension extension P f()

default implementation 
 for protocol/interface Swift Kotlin protocol P { func f() } extension P where … { func f() { /* do something */ } } interface I { fun f() { /* do something */ } } P f() extension
 where … P f()

default implementation 
 for protocol/interface Protocol Interface Implementation Implementation extension Swift Kotlin

Null safety Swift Kotlin let i: Int? i?.description if let i = i { i.description } val i: Int? i?.toString() if (i != null) { i.toString() }

Null safety Swift Kotlin let i: Int? i?.description if let i = i { i.description } val i: Int? i?.toString() if (i != null) { i.toString() } Optional Nullable

Null safety Swift Kotlin enum Optional { case none case some(Wrapped) } nullable Optional Nullable

Null safety Swift Kotlin enum Optional { case none case some(Wrapped) } nullable exist some value 
 or not null or not null Optional Nullable

Null safety Swift Kotlin ɹ exist some value 
 or not not null or null Value none or Value or null Optional Nullable

Null safety Swift Kotlin ɹ exist some value 
 or not not null or null Value none or Value or null Optional Nullable Value = Int?

Null safety Swift Kotlin ɹ exist some value 
 or not not null or null Int? none or Int? or null Optional Nullable Value = Int?

Null safety Swift Kotlin ɹ exist some value 
 or not not null or null 1 
 or
 nil none or 1 
 or
 null or null Optional Nullable Value = Int?

Null safety Swift Kotlin ɹ exist some value 
 or not not null or null .some
 (nil) none or or null null ?? Optional Nullable Value = Int?

Some familiar functions Swift Kotlin [1, 2, 3].forEach { if $0 == 2 { return } print($0) } listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) }

Some familiar functions Swift Kotlin [1, 2, 3].forEach { if $0 == 2 { return } print($0) } listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) }

[1, 2, 3].forEach { if $0 == 2 { return } print($0) } listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } Some familiar functions Swift Kotlin 1 3 1

[1, 2, 3].forEach { if $0 == 2 { return } print($0) } listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } Some familiar functions Swift Kotlin 1 3 1

Some familiar functions Swift Kotlin @_inlineable public func forEach( _ body: (Element) throws -> Void ) rethrows { for element in self { try body(element) } } public inline fun Iterable.forEach(action: (T) -> Unit): Unit { for (element in this) action(element) }

Some familiar functions Swift Kotlin @_inlineable public func forEach( _ body: (Element) throws -> Void ) rethrows { for element in self { try body(element) } } public inline fun Iterable.forEach(action: (T) -> Unit): Unit { for (element in this) action(element) }

Some familiar functions Swift Kotlin @_inlineable public func forEach( _ body: (Element) throws -> Void ) rethrows { for element in self { try body(element) } } public inline fun Iterable.forEach(action: (T) -> Unit): Unit { for (element in this) action(element) } inline: ݺͼग़͠ݩʹத਎Λల։ inline: ݺͼग़͠ݩʹத਎Λల։

Some familiar functions Swift Kotlin @_inlineable public func forEach( _ body: (Element) throws -> Void ) rethrows { for element in self { try body(element) } } public inline fun Iterable.forEach(action: (T) -> Unit): Unit { for (element in this) action(element) } inline: ϩδοΫʹӨڹ͠ͳ͍ inline: ϩδοΫʹӨڹ͢Δ

Some familiar functions Swift Kotlin @_inlineable public func forEach( _ body: (Element) throws -> Void ) rethrows { for element in self { try body(element) } } public inline fun Iterable.forEach(action: (T) -> Unit): Unit { for (element in this) action(element) } { if (it == 2) { return } println(it) } inline: ݺͼग़͠ݩʹத਎Λల։

Some familiar functions Kotlin listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } Iterable $receiver$iv = (Iterable)CollectionsKt.listOf(new Integer[] {Integer.valueOf(1), Integer.valueOf(2), Integer.valueOf(3)}); Iterator var2 = $receiver$iv.iterator(); while(var2.hasNext()) { Object element$iv = var2.next(); int it = ((Number)element$iv).intValue(); if(it == 2) { return; } System.out.println(it); }

Some familiar functions Kotlin listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } /* ... */ while(var2.hasNext()) { Object element$iv = var2.next(); int it = ((Number)element$iv).intValue(); if(it == 2) { return; } System.out.println(it); }

listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } /* ... */ while(var2.hasNext()) { Object element$iv = var2.next(); int it = ((Number)element$iv).intValue(); if(it == 2) { return; } System.out.println(it); } Some familiar functions Kotlin

listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } /* ... */ while(var2.hasNext()) { Object element$iv = var2.next(); int it = ((Number)element$iv).intValue(); if(it == 2) { return; } System.out.println(it); } Some familiar functions Kotlin non-local return

[1, 2, 3].forEach { if $0 == 2 { return } print($0) } listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } Some familiar functions Swift Kotlin 1 3 1

Kotlin OOP extension interface
 default implementati on generics delegation null safety tailrec static
 type Java GC sealed class variance
 declaration object JS companion 
 object if, when expression Type inference (Corout ines) inline annotation FP

Conclusion

• Started in 2010 • Object-oriented programming • Support functional programming • Static typing • Type inference • Null safety • Generic programming • Some syntax • Extension • Default implementation

&

Same word, different concept

Swift ͱ Kotlin ͲͪΒ΋ɺଞͷݴޠ͔Βػೳ΍ࢥ૝ΛऔΓೖΕ͍ͯΔ ͦΕΛͦΕͧΕʹݟ߹ͬͨܗͰ༥߹ͤͭͭ͞΋ɺ
 ֤ࣗͷจԽΛங͍͍ͯΔ ڞ௨͢Δ෦෼͸ੜ͡Δ

enjoy Swift, enjoy Kotlin :)

References Kotlin (official reference)
 https://kotlinlang.org/docs/reference/ The Swift Programming Language (Swift 4)
 https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/AboutTheLanguageReference.html Programming Kotlin
 by Stefan Bocutiu, Stephen Samuel Swift is like Kotlin: Hacker News (discussion)
 https://news.ycombinator.com/item?id=14364612 Swift is like Kotlin
 http://nilhcem.com/swift-is-like-kotlin/ SwiftKotlin
 https://github.com/angelolloqui/SwiftKotlin Swift vs Kotlin for real iOS/Android apps (ͱͯ΋ྑ͍هࣄͰͨ͠ʂ)
 http://angelolloqui.com/blog/38-Swift-vs-Kotlin-for-real-iOS-Android-apps Swift is NOT like Kotlin..?
 http://blog.applibot.co.jp/blog/2017/04/03/swift-is-not-like-kotlin/ iOSΞϓϦ։ൃऀ͔ΒݟͨKotlin (࣌ؒͷ౎߹Ͱল͍ͨ෦෼΋͋Γ·͕͢ɺߏจͷൺֱ͕៉ྷʹ·ͱ·͍ͬͯ·͢)
 https://speakerdeck.com/koishi/iosapurikai-fa-zhe-karajian-takotlin null҆શͰͳ͍ݴޠ͸ɺ΋͸΍ϨΨγʔݴޠͩ (nullable ͷछྨͱಛ௃)
 http://qiita.com/koher/items/e4835bd429b88809ab33#nullable-%E3%81%AE%E7%A8%AE%E9%A1%9E%E3%81%A8%E7%89%B9%E5%BE%B4 Android։ൃΛड஫͔ͨ͠ΒKotlinΛΨοπϦ࢖ͬͯΈͨΒ࠷ߴͩͬͨ
 http://qiita.com/omochimetaru/items/98e015b0b694dd97f323 ๩͍͠SwiftΤϯδχΞͷͨΊͷKotlinೖ໳
 https://speakerdeck.com/inamiy/mang-siiswiftenziniafalsetamefalsekotlinru-men Kotlin and Swift. Is it a whole new era in Mobile Development?
 https://medium.com/@andycherkashyn/kotlin-and-swift-is-it-a-new-mobile-development-era-b4c5e81feb08 Swift/Kotlin߹ಉษڧձ
 https://oi-study.connpass.com/event/62521/

Q & A

[1, 2, 3].forEach { if $0 == 2 { return } print($0) } listOf(1, 2, 3).forEach { if (it == 2) { return } println(it) } Some familiar functions Swift Kotlin 1 3 1 ࣭໰ Swift Έ͍ͨͳڍಈʹͰ͖Δʁ

A: ಗ໊ؔ਺Λ࢖͍·͢ listOf(1, 2, 3).forEach(fun(element: Int) { if (element == 2) { return } print(element) return }) ͜ͷ return ͸ಗ໊ؔ਺ͷ return ͘͢͝ৄ͍͠આ໌
 JavaϓϩάϥϚ͕KotlinͰͭ·͖͕ͮͪͳͱ͜Ζ
 http://qiita.com/koher/items/ d9411a00986f14683a3f#inline%2d%e3%81%a8%2dnon%2dlocal%2dreturn

ձ৔Ͱ౴͑ͯͩͬͨ͘͞ @omochimetaru ͞Μɺ
 هࣄΛࣥචɺπΠʔτ͍͖ͨͩ·ͨ͠ @koher ͞Μ
 ͋Γ͕ͱ͏͍͟͝·͢ʂ

Some familiar functions Swift @_inlineable public func first( where predicate: (Element) throws -> Bool ) rethrows -> Element? { var foundElement: Element? do { try self.forEach { if try predicate($0) { foundElement = $0 throw _StopIteration.stop } } } catch is _StopIteration { } return foundElement } ྫ֎౤͛ͯ୤ग़ ༨ஊ
 Swift Ͱ forEachൈ͚͍ͨͱ͖
 ྫ: first(where: )

࣭໰
 inline ࢦఆΛ͢Δ͜ͱʹΑΔϩδο ΫޡΓͷճආΛͲ͏͢Δ͔ ճ౴͸དྷिதʹΞοϓσʔτ͠·͢ʂ ><