2018-10-15-kotlin13

Kotlin Conf2018 報告会
Kotlin1.3新機能
@CA.kt

Transcript

1. AAkira @_a_akira
   Kotlin Conf2018報告会
   - Kotlin 1.3新機能-
   

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2. About me
   @_a_akira AAkira
   CyberAgent, Inc.
   Akira Aratani
   https://aakira.app
   !"#$%&'()*+,-./012345
   

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4. New Type Inference and Related Language Features
   Svetlana Isakova
   Svetlana Isakova has worked on the Kotlin language at
   JetBrains. She’s co-authored the book Kotlin in Action
   and now is a Developer Advocate, where she spends her
   time teaching Kotlin and speaking at conferences
   worldwide.
   

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5. Agenda
   • Experimental features
   • Contracts
   • New type Inference
   

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6. λΠτϧ
   Experimental features
   

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7. Experimental features
   Purpose
   To let new features be tried by early adopters 

   as soon as possible
   

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8. Experimental features
   Tools > Kotlin > Enable migrations detection (experimental)
   

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9. Experimental features
   Migration tool
   

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10. Experimental features
    experimentalの機能を使う場合はgradleに追加するする必要がある
    kotlin { 

    experimental { coroutines 'enable' }
    }
    

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11. Experimental features
    import kotlinx.coroutines.experimental.*
    import kotlinx.coroutines.*
    ˣ
    1.2
    1.3
    

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12. Experimental features
    自分でExperimental APIを作ることも可能
    @Experimental
    annotation class ShinyNewAPI
    

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13. Experimental features
    // Ϋϥεʹ΋෇͚ΒΕΔ
    @ShinyNewAPI
    class Foo {}
    // ؔ਺ʹ΋෇͚ΒΕΔ
    @ShinyNewAPI
    fun Foo.bar() = ""
    

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14. Experimental features
    @ShinyNewAPI
    fun doSomething() {
    val foo = Foo()
    foo.bar()
    }
    @ShinyNewAPI
    fun main() {
    doSomething()
    }
    

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15. Experimental features
    @ShinyNewAPI
    fun doSomething() {
    val foo = Foo()
    foo.bar()
    }
    @ShinyNewAPI
    fun main() {
    doSomething()
    }
    1.3からmain関数の引数はオプションになった
    

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16. Experimental features
    @ShinyNewAPI
    fun doSomething() {
    val foo = Foo()
    foo.bar()
    }
    @ShinyNewAPI
    fun main() {
    doSomething()
    }
    

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17. Experimental features
    @UseExperimental(ShinyNewAPI::class)
    fun doSomething() {
    val foo = Foo()
    foo.bar()
    }
    

    fun main() {
    doSomething()
    }
    

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18. Experimental features
    @UseExperimental(ShinyNewAPI::class)
    fun doSomething() {
    val foo = Foo()
    foo.bar()
    }
    

    fun main() {
    doSomething()
    }
    

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19. $POUSBDUT
    Contracts
    

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20. Kotlin Puzzler
    Kotlin1.2で実行する場合
    fun main(args: Array) {
    var hoge: Int?
    run {
    hoge = 46
    }
    println(hoge)
    }
    // a) 46
    // b) NullPointerException
    // c) null
    // d) Will not compile
    

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21. Kotlin Puzzler
    Kotlin 1.3より前では実行出来ない
    fun main(args: Array) {
    var hoge: Int?
    run {
    hoge = 46
    }
    println(hoge)
    }
    // a) 46
    // b) NullPointerException
    // c) null
    // d) Will not compile
    

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22. Kotlin Puzzler
    fun main(args: Array) {
    var hoge: Int?
    run {
    hoge = 46
    }
    println(hoge)
    }
    // a) 46
    // b) NullPointerException
    // c) null
    // d) Will not compile
    コンパイラは初期化されているのか、判断出来ない
    

    printの部分で “variable hoge must be initialized”
    

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23. Contracts
    // 1.3
    inline fun run(block: () -> R): R {
    contract {
    callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    return block()
    }
    // 1.2

    public inline fun run(block: () -> R): R = block()
    

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24. Contracts
    // 1.3
    inline fun run(block: () -> R): R {
    contract {
    callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    return block()
    }
    // 1.2

    public inline fun run(block: () -> R): R = block()
    

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25. Contracts
    • can be implicitly changed
    • can implicitly break code depending on it
    なぜコンパイラはrun内で代入されたhogeがnon-nullなのを理解出来ないのか
    

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26. Contracts
    // 1.3
    inline fun run(block: () -> R): R {
    contract {
    callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    return block()
    }
    // 1.2

    public inline fun run(block: () -> R): R = block()
    コンパイラに一度だけ実行されるという情報を

    教えてあげる
    

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27. Contracts
    Kotlin 1.3では実行可能
    fun main(args: Array) {
    var hoge: Int?
    run {
    hoge = 46
    }
    println(hoge)
    }
    

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28. Contracts
    Kotlin 1.3より前では実行出来ない
    fun main(args: Array) {

    val s : String? = ""
    if(!s.isNullOrEmpty()) {
    s.first()
    }

    }
    

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29. Contracts
    Kotlin 1.3より前では実行出来ない
    fun main(args: Array) {

    val s : String? = ""
    if(!s.isNullOrEmpty()) {
    s.first()
    }

    }
    sがnot nullだとはコンパイラは理解出来ない
    

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30. Contracts
    1.3でのisNullOrEmptyの実装
    public inline fun CharSequence?.isNullOrEmpty(): Boolean {
    contract {
    returns(false) implies (this@isNullOrEmpty != null)
    }
    return this == null || this.length == 0
    }
    

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31. Contracts
    1.3でのisNullOrEmptyの実装
    public inline fun CharSequence?.isNullOrEmpty(): Boolean {
    contract {
    returns(false) implies (this@isNullOrEmpty != null)
    }
    return this == null || this.length == 0
    } return falseの時に

    isNullOrEmpty != nullの情報を

    コンパイラに教える
    

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32. Contracts
    Kotlin 1.3では実行可能
    fun main(args: Array) {

    val s : String? = ""
    if(!s.isNullOrEmpty()) {
    s.first()
    }

    }
    

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33. Contracts
    自作も可能
    @ExperimentalContracts
    private inline fun CharSequence?.hoge(): Boolean {
    contract { returns(false) implies (this@hoge != null) }
    return this == null || this.length == 0
    }

    

    @ExperimentalContracts
    fun main() {
    var a: String? = "abc"
    if (!a.hoge()) {
    println(a.first())
    }
    }
    

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34. 自作も可能
    Contracts
    @ExperimentalContracts
    private inline fun CharSequence?.hoge(): Boolean {
    contract { returns(false) implies (this@hoge != null) }
    return this == null || this.length == 0
    }

    

    @ExperimentalContracts
    fun main() {
    var a: String? = "abc"
    if (!a.hoge()) {
    println(a.first())
    }
    }
    contractもExperimentalContracts annotationが必要
    

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35. Contracts
    @UseExperimental(ExperimentalContracts::class)
    private inline fun CharSequence?.hoge(): Boolean {
    contract { returns(false) implies (this@hoge != null) }
    return this == null || this.length == 0
    }
    fun main() {
    var a: String? = "abc"
    if (!a.hoge()) {
    println(a.first())
    }
    }
    UseExperimentalで書き換え可能
    

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36. Contracts
    @UseExperimental(ExperimentalContracts::class)
    private inline fun CharSequence?.hoge(): Boolean {
    contract { returns(false) implies (this@hoge != null) }
    return this == null || this.length == 0
    }
    fun main() {
    var a: String? = "abc"
    if (!a.hoge()) {
    println(a.first())
    }
    }
    ここでも、UseExperimental annotationが使える
    UseExperimentalで書き換え可能
    

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37. Contracts
    @UseExperimental(ExperimentalContracts::class)
    private inline fun CharSequence?.hoge(): Boolean {
    contract { returns(false) implies (this@hoge != null) }
    return this == null || this.length == 0
    }
    fun main() {
    var a: String? = "abc"
    if (!a.hoge()) {
    println(a.first())
    }
    }
    annotationが不要
    

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38. Contracts
    • run, let, with, apply, also, takeIf, takeUnless, synchronized
    • isNullOrEmpty, isNullOrBlank,
    • kotlin.test: assertTrue, assertFalse, assertNotNull
    • check, checkNotNull, require, requireNotNull
    Contractが追加されたメソッド達
    

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39. /FXUZQFJOGFSFODF
    New type inference
    

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40. New type inference
    kotlin { 

    experimental { newInference 'enable' }
    }
    

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41. New type inference
    • SAM conversions for Kotlin functions
    • Better inference for builders
    • Better inference for call chains
    • Better inference for intersection types
    

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42. public interface Action {
    void execute(T target);
    }
    SAM conversions
    .java
    fun handleInput(handler: Action) {
    ...
    }
    fun main() {
    handleInput(Action { target ->
    println(target) 

    })
    }
    .kt
    

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43. public interface Action {
    void execute(T target);
    }
    SAM conversions
    .java
    fun handleInput(handler: Action) {
    ...
    }
    fun main() {

    handleInput { println(it) }
    }
    .kt
    1.3からはこう書ける
    

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44. SAM conversions
    val obs = Observable.just(100)
    Observable.just(1)
    .zipWith(obs, BiFunction { a, b -> a + b })
    .subscribe { }
    RxJava2から第二引数でlamda式が使えなくなっていた

    => RxKotlin(https://github.com/ReactiveX/RxKotlin) で回避していた
    

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45. SAM conversions
    val obs = Observable.just(100)
    Observable.just(1)
    .zipWith(obs) { a, b -> a + b }
    .subscribe { }
    RxKotlinを使わなくても良くなった!
    

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46. Inference for builder lambdas
    val seq = sequence {
    yield(42)
    print("hoge")
    yield(4)
    }
    Kotlin1.3から型パラメータが不要
    

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47. Inference for builder lambdas
    Kotlin1.3から型パラメータが不要
    val seq = sequence {
    yield(42)
    print("hoge")
    yield(4)
    }
    

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48. Inference for builder lambdas
    fun buildList(
    init: MutableList.() -> Unit
    ): List {
    return mutableListOf().apply(init)
    }
    fun main() {
    val list = buildList {
    add(1)
    add(2)
    }
    }
    もちろん自分でも定義可能
    

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49. Inference for builder lambdas
    @UseExperimental(ExperimentalTypeInference::class)
    fun buildList(
    @BuilderInference init: MutableList.() -> Unit
    ): List {
    return mutableListOf().apply(init)
    }
    fun main() {
    val list = buildList {
    add(1)
    add(2)
    }
    }
    BuilderInference annotationを使う
    

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50. Inference for builder lambdas
    @UseExperimental(ExperimentalTypeInference::class)
    fun buildList(
    @BuilderInference init: MutableList.() -> Unit
    ): List {
    return mutableListOf().apply(init)
    }
    fun main() {
    val list = buildList {
    add(1)
    add(2)
    }
    }
    BuilderInference annotationを使う
    

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51. Inference for builder lambdas
    @UseExperimental(ExperimentalTypeInference::class)
    fun buildList(
    @BuilderInference init: MutableList.() -> Unit
    ): List {
    return mutableListOf().apply(init)
    }
    fun main() {
    val list = buildList {
    add(1)
    add(2)
    }
    }
    これによって1.3より前で
    

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52. Inference for builder lambdas
    @UseExperimental(ExperimentalTypeInference::class)
    fun buildList(
    @BuilderInference init: MutableList.() -> Unit
    ): List {
    return mutableListOf().apply(init)
    }
    fun main() {
    val list = buildList {
    add(1)
    add(2)
    }
    }
    Intを省略可能
    

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53. Inference for call chains
    fun createMap(): Map = MapBuilder()
    .put("answer", 42)
    .build()
    MapBuilderは自分で定義した関数? (発表資料ままです)
    Kotlin 1.2: One call is analyzed at a time

    Kotlin 1.3: A call chain is analyzed
    

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54. Inference for call chains
    fun createMap() = MapBuilder()
    .put("answer", 42)
    .build()
    Kotlin1.3からは全体で評価されるので型定義を省略可能
    

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55. Intersection types
    interface Foo
    interface Bar
    fun hoge(thing: T) where T : Foo, T : Bar {
    println(thing)
    }
    fun better() {
    val something: Better = Better.A
    if (something is Foo && something is Bar) {
    hoge(something) // Foo & Bar
    }
    }
    sealed class Better {
    object A : Better()
    object B : Better(), Foo
    object C : Better(), Foo, Bar
    }
    

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56. Intersection types
    interface Foo
    interface Bar
    fun hoge(thing: T) where T : Foo, T : Bar {
    println(thing)
    }
    fun better() {
    val something: Better = Better.A
    if (something is Foo && something is Bar) {
    hoge(something) // Foo & Bar
    }
    }
    sealed class Better {
    object A : Better()
    object B : Better(), Foo
    object C : Better(), Foo, Bar
    }
    

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57. Intersection types
    interface Foo
    interface Bar
    fun hoge(thing: T) where T : Foo, T : Bar {
    println(thing)
    }
    fun better() {
    val something: Better = Better.A
    if (something is Foo && something is Bar) {
    hoge(something) // Foo & Bar
    }
    }
    sealed class Better {
    object A : Better()
    object B : Better(), Foo
    object C : Better(), Foo, Bar
    }
    somethingは Foo & Barと判定しているが…
    

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58. Intersection types
    interface Foo
    interface Bar
    fun hoge(thing: T) where T : Foo, T : Bar {
    println(thing)
    }
    fun better() {
    val something: Better = Better.A
    if (something is Foo && something is Bar) {
    hoge(something) // Compile error
    }
    }
    sealed class Better {
    object A : Better()
    object B : Better(), Foo
    object C : Better(), Foo, Bar
    }
    Kotlin1.2まではコンパイルエラーだった
    

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59. Intersection types
    interface Foo
    interface Bar
    fun hoge(thing: T) where T : Foo, T : Bar {
    println(thing)
    }
    fun better() {
    val something: Better = Better.A
    if (something is Foo && something is Bar) {
    hoge(something) // Foo & Bar
    }
    }
    sealed class Better {
    object A : Better()
    object B : Better(), Foo
    object C : Better(), Foo, Bar
    }
    1.3からはコンパイル可
    

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60. 4VNNBSZ
    Summary
    

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61. Summary
    • Experimentalの役割がより明確に
    • Kotlin1.3は痒かったところに手が届く

    - Contracts

    - SAM

    - Inference
    • KotlinConf 凄く良かった

    個人的にはKotlin Nativeを激推ししていきたい
    

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62. AAkira @_a_akira
    Have a nice Kotlin
    

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