Effective Swift-Kotlin Interoperability (KotlinConf 2019)

Over the past year, Multiplatform Fever has swept the world with the promise of code sharing between iOS and Android codebases. But how does it *really* work? What compromises have to be made by both platforms in order to achieve this goal?

This talk will make a deep comparison of Swift vs. Kotlin, you’d need a deep understanding of both languages

Some topics that would be covered:
* How do Swift consumers interact with Kotlin code (for example, generics)
* What problems does ObjC bring to the table?
* Fundamental differences between Swift and Kotlin today (value types/structures vs data classes, enums with associated values vs sealed classes)
* performance implications (build and runtime)
* current problems + best practices to avoid them

Attendees will leave this talk with a better understanding of what problems still exist, yet feel encouraged to start dabbling in their current codebases.

Video: https://youtu.be/Ij9guIZ-vBY?t=22180

1. Copenhagen Denmark EFFECTIVE SWIFT- KOTLIN INTEROPERABILITY JOHN RODRIGUEZ @jrodbx
5. @objc
9. include ':app' settings.gradle settings.gradle
10. include ':app' include ':SharedCode' settings.gradle
11. plugins { kotlin("multiplatform") } kotlin { … iOSTarget("ios") { binaries { framework { baseName = "ESKIOFramework" } } } jvm("android") sourceSets["commonMain"].dependencies { implementation("org.jetbrains.kotlin:kotlin-stdlib-common") SharedCode/build.gradle.kts
12. } } jvm("android") sourceSets["commonMain"].dependencies { implementation("org.jetbrains.kotlin:kotlin-stdlib-common") } sourceSets["androidMain"].dependencies { implementation("org.jetbrains.kotlin:kotlin-stdlib") } } val packForXcode by tasks.creating(Sync::class) { val targetDir = File(buildDir, "xcode-frameworks") /// selecting the right configuration for the iOS /// framework depending on the environment /// variables set by Xcode build val mode = System.getenv("CONFIGURATION") ?: "DEBUG" val framework = kotlin.targets .getByName<KotlinNativeTarget>("ios") SharedCode/build.gradle.kts
13. implementation("org.jetbrains.kotlin:kotlin-stdlib") } } val packForXcode by tasks.creating(Sync::class) { val targetDir = File(buildDir, "xcode-frameworks") … val framework = kotlin.targets .getByName<KotlinNativeTarget>("ios") .binaries.getFramework(…) dependsOn(framework.linkTask) from({ framework.outputDirectory }) into(targetDir) … } tasks.getByName("build").dependsOn(packForXcode) SharedCode/build.gradle.kts
23. http://bit.ly/2RvF72h
25. ipa apk
26. jar framework aar actual/expect expect/actual SharedCode ipa apk
27. apk ipa jar framework aar aar jar Klib actual/expect expect/actual SharedCode actual/expect expect/actual Gradle dependencies
29. object Object class Clazz interface Interface { fun member() {} } SharedCode/src/commonMain/kotlin/demoCommon.kt
30. object Object class Clazz interface Interface { fun member() {} } let obj1 = Object() print(address(o: obj1)) let obj2 = Object() print(address(o: obj2)) let class1 = Clazz() print(address(o: class1)) let class2 = Clazz() print(address(o: class2))
31. object Object class Clazz interface Interface { fun member() {} } let obj1 = Object() print(address(o: obj1)) let obj2 = Object() print(address(o: obj2)) let class1 = Clazz() print(address(o: class1)) let class2 = Clazz() print(address(o: class2)) 105553140519616 105553140519616 105553140519264 105553140519072
32. @interface KotlinBase : NSObject - (instancetype)init __attribute__((unavailable)); + (instancetype)new __attribute__((unavailable)); + (void)initialize __attribute__((objc_requires_super)); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Object"))) @interface ESKIOFObject : KotlinBase + (instancetype)object __attribute__((swift_name("init()"))); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Clazz"))) @interface ESKIOFClazz : KotlinBase - (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer)); @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
33. @interface KotlinBase : NSObject - (instancetype)init __attribute__((unavailable)); + (instancetype)new __attribute__((unavailable)); + (void)initialize __attribute__((objc_requires_super)); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Object"))) @interface ESKIOFObject : KotlinBase + (instancetype)object __attribute__((swift_name("init()"))); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Clazz"))) @interface ESKIOFClazz : KotlinBase - (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer)); @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
34. @interface KotlinBase : NSObject - (instancetype)init __attribute__((unavailable)); + (instancetype)new __attribute__((unavailable)); + (void)initialize __attribute__((objc_requires_super)); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Object"))) @interface ESKIOFObject : KotlinBase + (instancetype)object __attribute__((swift_name("init()"))); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Clazz"))) @interface ESKIOFClazz : KotlinBase - (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer)); @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
35. @interface KotlinBase : NSObject - (instancetype)init __attribute__((unavailable)); + (instancetype)new __attribute__((unavailable)); + (void)initialize __attribute__((objc_requires_super)); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Object"))) @interface ESKIOFObject : KotlinBase + (instancetype)object __attribute__((swift_name("init()"))); @end; __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("Clazz"))) @interface ESKIOFClazz : KotlinBase - (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer)); @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
36. fun plusplus(value: Int): Int { return value + 1 } SharedCode/src/commonMain/kotlin/demoCommon.kt
37. fun plusplus(value: Int): Int { return value + 1 } let value = 5 DemoCommonKt.plusplus(value: value)
38. let value = 5 DemoCommonKt.plusplus(value: value) fun plusplus(value: Int): Int { return value + 1 } Cannot convert value … 'Int' to … 'Int32' _
39. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("DemoCommonKt"))) @interface ESKIOFDemoCommonKt : KotlinBase … + (int32_t)plusplusValue:(int32_t)value __attribute__((swift_name("plusplus(value:)"))); … @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
40. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("DemoCommonKt"))) @interface ESKIOFDemoCommonKt : KotlinBase … + (int32_t)plusplusValue:(int32_t)value __attribute__((swift_name("plusplus(value:)"))); … @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
41. let value = 5 DemoCommonKt.plusplus(value: value) fun plusplus(value: Int): Int { return value + 1 } Cannot convert value … 'Int' to … 'Int32' _
42. let value = 5 as Int32 DemoCommonKt.plusplus(value: value) fun plusplus(value: Int): Int { return value + 1 } Cannot convert value … 'Int' to … 'Int32' _
43. let value = 5 as Int32 DemoCommonKt.plusplus(value: value) fun plusplus(value: Int): Int { return value + 1 } Cannot convert value … 'Int' to … 'Int32' _
44. fun plusplus(value: Int): Intx{ return valuex+x1 } let value = 5 as Int32 DemoCommonKt.plusplus(value: value)
45. fun plusplus(value: Int) = valuex+x1 fun plusplus(value: Long) = value + 1 fun plusplus(value: Double) = value + 1 fun plusplus(value: Float) = value + 1 let value = 5 as Int32 DemoCommonKt.plusplus(value: value)
46. fun plusplus(value: Int) = valuex+x1 fun plusplus(value: Long) = value + 1 fun plusplus(value: Double) = value + 1 fun plusplus(value: Float) = value + 1 let iValue = 5 as Int32 let lValue = 5 as Int64 let dValue = 5.0 let fValue: Float = 5.0 DemoCommonKt.plusplus(value__: iValue) DemoCommonKt.plusplus(value___: lValue) DemoCommonKt.plusplus(value: dValue) DemoCommonKt.plusplus(value_: fValue)
47. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("DemoCommonKt"))) @interface ESKIOFDemoCommonKt : KotlinBase … + (double)plusplusValue:(double)value __attribute__((swift_name("plusplus(value:)"))); + (float)plusplusValue_:(float)value __attribute__((swift_name("plusplus(value_:)"))); + (int32_t)plusplusValue__:(int32_t)value __attribute__((swift_name("plusplus(value__:)"))); + (int64_t)plusplusValue___:(int64_t)value __attribute__((swift_name("plusplus(value___:)"))); … @end; KotliniOS/Frameworks/ESKIOFramework.framework/Headers/ESKIOFramework.h
48. fun plusplus(value: Int) = valuex+x1 fun plusplus(value: Long) = value + 1 fun plusplus(value: Double) = value + 1 fun plusplus(value: Float) = value + 1 let iValue = 5 as Int32 let lValue = 5 as Int64 let dValue = 5.0 let fValue: Float = 5.0 DemoCommonKt.plusplus(value__: iValue) DemoCommonKt.plusplus(value___: lValue) DemoCommonKt.plusplus(value: dValue) DemoCommonKt.plusplus(value_: fValue)
49. fun plusplus(intValue: Int) = intValue +x1 fun plusplus(longValue: Long) = longValue + 1 fun plusplus(doubleValue: Double) = doubleValue + 1 fun plusplus(floatValue: Float) = floatValue + 1 let iValue = 5 as Int32 let lValue = 5 as Int64 let dValue = 5.0 let fValue: Float = 5.0 DemoCommonKt.plusplus(intValue: iValue) DemoCommonKt.plusplus(longValue: lValue) DemoCommonKt.plusplus(doubleValue: dValue) DemoCommonKt.plusplus(floatValue: fValue)
50. Compromises
51. Lack of Common Library Support*
53. Okio OkHttp Moshi Wire IO HTTP Client serialization
54. Okio OkHttp IO HTTP Client serialization Moshi? Wire
55. Okio OkHttp Moshi? Wire IO HTTP Client serialization DB SqlDelight
57. Avoid UI Layer
60. Language Features
61. enum class City { NEW_YORK, CHICAGO, NAPLES }
62. __attribute__((swift_name("City"))) @interface ESKIOFCity : ESKIOFKotlinEnum //… @property (class, readonly) ESKIOFCity *theNewYork __attribute__((swift_name("theNewYork"))); @property (class, readonly) ESKIOFCity *chicago __attribute__((swift_name("chicago"))); @property (class, readonly) ESKIOFCity *naples __attribute__((swift_name("naples"))); - (instancetype)initWithName:(NSString *)name ordinal:(int32_t)ordinal __attribute__((swift_name("init(name:ordinal:)"))); - (int32_t)compareToOther:(ESKIOFCity *)other __attribute__((swift_name("compareTo(other:)"))); @end;
63. __attribute__((swift_name("City"))) @interface ESKIOFCity : ESKIOFKotlinEnum //… @property (class, readonly) ESKIOFCity *theNewYork __attribute__((swift_name("theNewYork"))); @property (class, readonly) ESKIOFCity *chicago __attribute__((swift_name("chicago"))); @property (class, readonly) ESKIOFCity *naples __attribute__((swift_name("naples"))); - (instancetype)initWithName:(NSString *)name ordinal:(int32_t)ordinal __attribute__((swift_name("init(name:ordinal:)"))); - (int32_t)compareToOther:(ESKIOFCity *)other __attribute__((swift_name("compareTo(other:)"))); @end;
64. enum class City { NEW_YORK, CHICAGO, NAPLES }
65. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City.chicago switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .theNewYork: print("New York!") }
66. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City.chicago switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .theNewYork: print("New York!") } Switch must be exhaustive. _
67. __attribute__((swift_name("City"))) @interface ESKIOFCity : ESKIOFKotlinEnum //… @property (class, readonly) ESKIOFCity *theNewYork __attribute__((swift_name("theNewYork"))); @property (class, readonly) ESKIOFCity *chicago __attribute__((swift_name("chicago"))); @property (class, readonly) ESKIOFCity *naples __attribute__((swift_name("naples"))); - (instancetype)initWithName:(NSString *)name ordinal:(int32_t)ordinal __attribute__((swift_name("init(name:ordinal:)"))); - (int32_t)compareToOther:(ESKIOFCity *)other __attribute__((swift_name("compareTo(other:)"))); @end;
68. __attribute__((swift_name("City"))) @interface ESKIOFCity : ESKIOFKotlinEnum //… @property (class, readonly) ESKIOFCity *theNewYork __attribute__((swift_name("theNewYork"))); @property (class, readonly) ESKIOFCity *chicago __attribute__((swift_name("chicago"))); @property (class, readonly) ESKIOFCity *naples __attribute__((swift_name("naples"))); - (instancetype)initWithName:(NSString *)name ordinal:(int32_t)ordinal __attribute__((swift_name("init(name:ordinal:)"))); - (int32_t)compareToOther:(ESKIOFCity *)other __attribute__((swift_name("compareTo(other:)"))); @end;
69. __attribute__((swift_name("KotlinEnum"))) @interface ESKIOFKotlinEnum : KotlinBase <ESKIOFKotlinComparable> - (instancetype)initWithName:(NSString *)name ordinal:(int32_t)ordinal __attribute__((swift_name("init(name:ordinal:)"))) __attribute__((objc_designated_initializer)); - (int32_t)compareToOther:(ESKIOFKotlinEnum *)other __attribute__((swift_name("compareTo(other:)"))); - (BOOL)isEqual:(id _Nullable)other __attribute__((swift_name("isEqual(_:)"))); - (NSUInteger)hash __attribute__((swift_name("hash()"))); - (NSString *)description __attribute__((swift_name("description()"))); @property (readonly) NSString *name __attribute__((swift_name("name"))); @property (readonly) int32_t ordinal __attribute__((swift_name("ordinal"))); @end;
70. __attribute__((swift_name("KotlinEnum"))) @interface ESKIOFKotlinEnum : KotlinBase <ESKIOFKotlinComparable> - (instancetype)initWithName:(NSString *)name ordinal:(int32_t)ordinal __attribute__((swift_name("init(name:ordinal:)"))) __attribute__((objc_designated_initializer)); - (int32_t)compareToOther:(ESKIOFKotlinEnum *)other __attribute__((swift_name("compareTo(other:)"))); - (BOOL)isEqual:(id _Nullable)other __attribute__((swift_name("isEqual(_:)"))); - (NSUInteger)hash __attribute__((swift_name("hash()"))); - (NSString *)description __attribute__((swift_name("description()"))); @property (readonly) NSString *name __attribute__((swift_name("name"))); @property (readonly) int32_t ordinal __attribute__((swift_name("ordinal"))); @end;
71. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City.chicago switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .theNewYork: print("New York!") } Switch must be exhaustive. _
72. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City.chicago switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .theNewYork: print("New York!") default: fatalError("This can't be reached") }
74. enum City: RawRepresentable {a … }b
75. enum City: RawRepresentable {a case chicago case newyork case naples init(rawValue: ESKIOFramework.City) { switch (rawValue){ case .theNewYork: self = .newyork case .chicago: self = .chicago case .naples: self = .naples default: fatalError("This can't be reached") } } var rawValue: ESKIOFramework.City { switch(self){ case .newyork: return .theNewYork case .chicago: return .chicago case .naples: return .naples } } }b
76. enum City: RawRepresentable {a case chicago case newyork case naples init(rawValue: ESKIOFramework.City) { switch (rawValue){ case .theNewYork: self = .newyork case .chicago: self = .chicago case .naples: self = .naples default: fatalError("This can't be reached") } } var rawValue: ESKIOFramework.City { switch(self){ case .newyork: return .theNewYork case .chicago: return .chicago case .naples: return .naples } } }b
77. enum City: RawRepresentable {a case chicago case newyork case naples case unknown init(rawValue: ESKIOFramework.City) { switch (rawValue){ case .theNewYork: self = .newyork case .chicago: self = .chicago case .naples: self = .naples default: self = .unknown } } var rawValue: ESKIOFramework.City { switch(self){ case .newyork: return .theNewYork case .chicago: return .chicago case .naples: return .naples case .unknown: fatalError("This should never happen!") } }
78. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City.chicago switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .theNewYork: print("New York!") default: fatalError("This can't be reached") }
79. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City.chicago switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .newyork: print("New York!") }
80. enum class City { NEW_YORK, CHICAGO, NAPLES } let city = City(rawValue: ESKIOFramework.City.chicago) switch city { case .chicago: print("Chicago!") case .naples: print("Naples!") case .newyork: print("New York!") }
81. enum class City { NEW_YORK, CHICAGO, NAPLES, ANYWHERE } sealed class Pizza(val city: City) { object ThinCrust : Pizza(NEW_YORK) object DeepDish : Pizza(CHICAGO) object Neapolitan : Pizza(NAPLES) class Dessert(val topping: String): Pizza(ANYWHERE) }
82. enum City: RawRepresentable {a case chicago case newyork case naples init(rawValue: ESKIOFramework.City) { switch (rawValue){ case .theNewYork: self = .newyork case .chicago: self = .chicago case .naples: self = .naples default: fatalError("This can't be reached") } } var rawValue: ESKIOFramework.City { switch(self){ case .newyork: return .theNewYork case .chicago: return .chicago case .naples: return .naples } } }b
83. enum City: RawRepresentable {a case chicago case newyork case naples case anywhere init(rawValue: ESKIOFramework.City) { switch (rawValue){ case .theNewYork: self = .newyork case .chicago: self = .chicago case .naples: self = .naples case .anywhere: self = .anywhere default: fatalError("This can't be reached") } } var rawValue: ESKIOFramework.City { switch(self){ case .newyork: return .theNewYork case .chicago: return .chicago case .naples: return .naples case .anywhere: return .anywhere }
84. enum Pizza: RawRepresentable {a }b
85. enum Pizza: RawRepresentable {a case deepdish(City) case thin(City) case neapolitan(City) case dessert(City, String) }b
86. enum Pizza: RawRepresentable {a … init(rawValue: ESKIOFramework.Pizza) { switch (rawValue){ case .DeepDish(): self = .deepdish(City(rawValue: rawValue.city)) … case is ESKIOFramework.Pizza.Dessert: let dessert = (rawValue as! ESKIOFramework.Pizza.Dessert) self = .dessert(City(rawValue: rawValue.city), dessert.topping) default: fatalError("This can't be reached") } } var rawValue: ESKIOFramework.Pizza { switch(self){ case .deepdish: return .DeepDish() … case let .dessert(_, topping): return ESKIOFramework.Pizza.Dessert(topping: topping) } } }b
87. func printCity(city: City) { switch city { case .naples: print("Naples!") case .chicago: print("Chicago!") case .newyork: print("New Yawk!") case .anywhere: print("Anywhere!") } } func printPizza(pizza: Pizza) { switch pizza { case let .neapolitan(city): print("City: \(city)") case let .deepdish(city): print("City: \(city)") case let .thin(city): print("City: \(city)") case let .dessert(city, topping): print("City: \(city), Dessert: \(topping)") } }
88. New Yawk! Chicago! Naples! Anywhere! City: newyork City: naples City: chicago City: anywhere, Dessert: nutella
90. Generics
91. class StateHolder<T>(state: T) { val myState = state fun pullState(): T = myState }
92. class StateHolder<T>(state: T) { val myState = state fun pullState(): T = myState } let holder = StateHolder(state: "yo") let state = holder.pullState() print(state)
93. class StateHolder<T>(state: T) { val myState = state fun pullState(): T = myState } let holder = StateHolder(state: "yo") let state = holder.pullState() print(state) Expression implicitly coerced `Any?` To `Any` _ .
94. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("StateHolder"))) @interface ESKIOFStateHolder : KotlinBase - (instancetype)initWithState:(id _Nullable)state __attribute__((swift_name("init(state:)"))) __attribute__((objc_designated_initializer)); - (id _Nullable)pullState __attribute__((swift_name("pullState()"))); @property (readonly) id _Nullable myState __attribute__((swift_name("myState"))); @end;
95. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("StateHolder"))) @interface ESKIOFStateHolder : KotlinBase - (instancetype)initWithState:(id _Nullable)state __attribute__((swift_name("init(state:)"))) __attribute__((objc_designated_initializer)); - (id _Nullable)pullState __attribute__((swift_name("pullState()"))); @property (readonly) id _Nullable myState __attribute__((swift_name("myState"))); @end;
96. class StateHolder<T>(state: T) { val myState = state fun pullState(): T = myState } let holder = StateHolder(state: "yo") let state = holder.pullState() print(state) Expression implicitly coerced `Any?` To `Any` _ .
97. class StateHolder<T: Any>(state: T) { val myState = state fun pullState(): T = myState } let holder = StateHolder(state: "yo") let state = holder.pullState() print(state)
98. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("StateHolder"))) @interface ESKIOFStateHolder : KotlinBase - (instancetype)initWithState:(id _Nullable)state __attribute__((swift_name("init(state:)"))) __attribute__((objc_designated_initializer)); - (id _Nullable)pullState __attribute__((swift_name("pullState()"))); @property (readonly) id _Nullable myState __attribute__((swift_name("myState"))); @end;
99. __attribute__((objc_subclassing_restricted)) __attribute__((swift_name("StateHolder"))) @interface ESKIOFStateHolder : KotlinBase - (instancetype)initWithState:(id)state __attribute__((swift_name("init(state:)"))) __attribute__((objc_designated_initializer)); - (id)pullState __attribute__((swift_name("pullState()"))); @property (readonly) id myState __attribute__((swift_name("myState"))); @end;
100. class StateHolder<out T>(state: T) {…} fun copy(from: StateHolder<out Any>, to: StateHolder<Any>) {…} @interface ESKIOFStateHolder<__covariant T>
103. value types
104. struct Address { varaline1: String varaline2: String? varacity: String varastate: String varazip: String }a
105. struct Address {…}a func test() { var me = Address( line1: "1455 Market St", line2: "Apt 1", city: "San Francisco", state: "CA", zip: "94103" ) var neighbor = me neighbor.line2 = "Apt 2" print("\(me ?? ""), \(neighbor ?? "")") // prints "Apt 1, Apt 2" }
106. class Person { var firstName: String = "John" var lastName: String = "Doe" } func test() { var john = Person() var jane = john jane.firstName = "Jane" print("\(john.firstName), \(jane.firstName)") // oops, both "Jane" }
107. struct Address { varaline1: String varaline2: String? varacity: String varastate: String varazip: String }a
108. data class Address( val line1: String, val line2: String?, val city: String, val state: String, val zip: String )
109. data class Address(…) fun test() { val me = Address( line1 = "1455 Market St", line2 = "Apt 1", city = "San Francisco", state = "CA", zip = "94103" ) val neighbor = me.copy(line2 = "Apt 2") print("$me, $neighbor") }
110. struct Struct { var name: String } let a = Struct(name: "jrod") a.name = "" data class Struct(var name: String) val a = Struct(name = "jrod") a.name = "" Cannot assign …: 'a' is a 'let' constant _
111. class Point( val x: Int, val y: Int )
112. class Point( val x: Int, val y: Int ) value class Point( val x: Int, val y: Int ) Today Someday?
113. header header x y header x y header x y header x y val points = arrayOf(Point(1, 2), …)
114. header x x x x y y y y val points = arrayOf(Point(1, 2), …)
117. Build performance
123. $ ./gradlew :SharedCode:packForXCode \
 -—profile --rerun-tasks -—no-build-cache -—console=plain
124. $ ./gradlew :SharedCode:packForXCode \
 -—profile --rerun-tasks -—no-build-cache -—console=plain
128. http://bit.ly/34ZN5UQ
129. https://github.com/JetBrains/kotlin/blob/master/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/ jetbrains/kotlin/gradle/tasks/Tasks.kt#L128
130. Runtime performance
131. fun mergesort(list: List<Int>): List<Int> { if (list.size <= 1) return list val middle = list.size / 2 val left = list.subList(0, middle) val right = list.subList(middle, list.size) return merge(mergesort(left), mergesort(right)) } fun merge(left: List<Int>, right: List<Int>): List<Int> { var iLeft = 0 var iRight = 0 val newList = mutableListOf<Int>() while (iLeft < left.size && iRight < right.size) { if (left[iLeft] <= right[iRight]) newList.add(left[iLeft++]) else newList.add(right[iRight++]) } while (iLeft < left.size) newList.add(left[iLeft++]) while (iRight < right.size) newList.add(right[iRight++]) return newList }
144. https://bit.ly/32DOCyf
148. Recap
149. • Beware of Int! (Swift -> Kotlin)
150. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names
151. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries!
152. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story
153. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?!
154. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?! • On the other hand, Generics seem to favor Obj-C more
155. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?! • On the other hand, Generics seem to favor Obj-C more • No matter what progress is made, lack of value types is still a limiting factor
156. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?! • On the other hand, Generics seem to favor Obj-C more • No matter what progress is made, lack of value types is still a limiting factor • Build performance could be better, looking forward to native compiler improvements in 1.4
157. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?! • On the other hand, Generics seem to favor Obj-C more • No matter what progress is made, lack of value types is still a limiting factor • Build performance could be better, looking forward to native compiler improvements in 1.4 • Need that build cache issue fix removing @LocalState!
158. • Beware of Int! (Swift -> Kotlin) • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?! • On the other hand, Generics seem to favor Obj-C more • No matter what progress is made, lack of value types is still a limiting factor • Build performance could be better, looking forward to native compiler improvements in 1.4 • Need that build cache issue fix removing @LocalState! • Runtime performance isn't too bad for normal app cases, but heavy computation pays a heavier price
159. • Beware of Method overloads with similar parameter names • Let's continue to grow the core Multiplatform suite of libraries! • Enums matter! But currently a sore spot in today's interop story • JetBrains Swift Codegen?! • On the other hand, Generics seem to favor Obj-C more • No matter what progress is made, lack of value types is still a limiting factor • Build performance could be better, looking forward to native compiler improvements in 1.4 • Need that build cache issue fix removing @LocalState! • Runtime performance isn't too bad for normal app cases, but heavy computation pays a heavier price * Future continues to look promising for Swift-ObjC-Kotlin interop. Wire support for iOS a target for 2020.
160. @jrodbx
161. #KotlinConf THANK YOU AND REMEMBER TO VOTE John Rodriguez @jrodbx