What's up next for Kotlin? RC Edition

Transcript

1. What’s up next for Kotlin? Nicola Corti @cortinico RC Edition.

2. 1.3

3. 1.3

4. 1.3

5. Coroutines

6. Coroutines kotlin { experimental.coroutines = Coroutines.ENABLE }

7. Coroutines import kotlinx.coroutines.experimental.delay import kotlinx.coroutines.experimental.launch fun justACoroutine() { launch {

   delay(1000) println("Hello world!") } }

8. Coroutines import kotlinx.coroutines.delay import kotlinx.coroutines.launch fun justACoroutine() { launch {

   delay(1000) println("Hello world!") } }

9. Capturing When

10. Capturing When fun Request.getBody() : ResponseBody { val response =

    executeRequest() when (response) { is Authenticator.Success -> response.body is HttpError -> throw HttpException(response.status) } }

11. Capturing When fun Request.getBody() : ResponseBody { when (val response

    = executeRequest()) { is Authenticator.Success -> response.body is HttpError -> throw HttpException(response.status) } }

12. Capturing When fun Request.getBody() = when (val response = executeRequest())

    { is Authenticator.Success -> response.body is HttpError -> throw HttpException(response.status) }

13. Capturing When

14. KEEP

15. KEEP

16. Arity

17. Arity fun arity22Function(lambda : ( Int, Int, Int, Int, Int,

    Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) -> Unit) { }

18. Arity fun arity22Function(lambda : ( Int, Int, Int, Int, Int,

    Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) -> Unit) { } public final void arity22Function(@NotNull Function22 lambda) { Intrinsics.checkParameterIsNotNull(lambda, "lambda"); }

19. Arity package kotlin.jvm.functions /** A function that takes 0 arguments.

    */ public interface Function0<out R> : Function<R> { /** Invokes the function. */ public operator fun invoke(): R } /** A function that takes 1 argument. */ public interface Function1<in P1, out R> : Function<R> { /** Invokes the function with the specified argument. */ public operator fun invoke(p1: P1): R } /** A function that takes 2 arguments. */ public interface Function2<in P1, in P2, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2): R } /** A function that takes 3 arguments. */ public interface Function3<in P1, in P2, in P3, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3): R } /** A function that takes 4 arguments. */ public interface Function4<in P1, in P2, in P3, in P4, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4): R } /** A function that takes 5 arguments. */ public interface Function5<in P1, in P2, in P3, in P4, in P5, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5): R } /** A function that takes 6 arguments. */ public interface Function6<in P1, in P2, in P3, in P4, in P5, in P6, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6): R } /** A function that takes 7 arguments. */ public interface Function7<in P1, in P2, in P3, in P4, in P5, in P6, in P7, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7): R } /** A function that takes 8 arguments. */ public interface Function8<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8): R } /** A function that takes 9 arguments. */ public interface Function9<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9): R } /** A function that takes 10 arguments. */ public interface Function10<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10): R } /** A function that takes 11 arguments. */ public interface Function11<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, out R> : Function<R> {

20. Arity /** A function that takes 8 arguments. */ public

    interface Function8<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8): R } /** A function that takes 9 arguments. */ public interface Function9<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9): R } /** A function that takes 10 arguments. */ public interface Function10<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10): R } /** A function that takes 11 arguments. */ public interface Function11<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11): R } /** A function that takes 12 arguments. */ public interface Function12<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12): R } /** A function that takes 13 arguments. */ public interface Function13<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13): R } /** A function that takes 14 arguments. */ public interface Function14<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14): R } /** A function that takes 15 arguments. */ public interface Function15<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15): R } /** A function that takes 16 arguments. */ public interface Function16<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16): R } /** A function that takes 17 arguments. */ public interface Function17<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, in P17, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16, p17: P17): R } /** A function that takes 18 arguments. */ public interface Function18<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, in P17, in P18, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16, p17: P17, p18: P18): R } /** A function that takes 19 arguments. */ public interface Function19<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, in P17, in P18, in P19, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16, p17: P17, p18: P18, p19: P19): R } /** A function that takes 20 arguments. */ public interface Function20<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, in P17, in P18, in P19, in P20, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16, p17: P17, p18: P18, p19: P19, p20: P20): R } /** A function that takes 21 arguments. */ public interface Function21<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, in P17, in P18, in P19, in P20, in P21, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16, p17: P17, p18: P18, p19: P19, p20: P20, p21: P21): R } /** A function that takes 22 arguments. */ public interface Function22<in P1, in P2, in P3, in P4, in P5, in P6, in P7, in P8, in P9, in P10, in P11, in P12, in P13, in P14, in P15, in P16, in P17, in P18, in P19, in P20, in P21, in P22, out R> : Function<R> { /** Invokes the function with the specified arguments. */ public operator fun invoke(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6, p7: P7, p8: P8, p9: P9, p10: P10, p11: P11, p12: P12, p13: P13, p14: P14, p15: P15, p16: P16, p17: P17, p18: P18, p19: P19, p20: P20, p21: P21, p22: P22): R }

21. Arity fun arity22Function(lambda : ( Int, Int, Int, Int, Int,

    Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) -> Unit) { }

22. Arity fun arity23Function(lambda : ( Int, Int, Int, Int, Int,

    Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) -> Unit) { }

23. Arity fun arity23Function(lambda : ( Int, Int, Int, Int, Int,

    Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) -> Unit) { } public final void arity23Function(@NotNull FunctionN lambda) { Intrinsics.checkParameterIsNotNull(lambda, "lambda"); }

24. Arity fun arity23Function(lambda : ( Int, Int, Int, Int, Int,

    Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) -> Unit) { } public final void arity23Function(@NotNull FunctionN lambda) { Intrinsics.checkParameterIsNotNull(lambda, "lambda"); }

25. Arity @SinceKotlin("1.3") interface FunctionN<out R> : Function<R>, FunctionBase<R> { /**

    * Invokes the function with the specified arguments. * * Must **throw exception** if the length of passed [args] * is not equal to the parameter count returned by [arity]. * * @param args arguments to the function */ operator fun invoke(vararg args: Any?): R /** * Returns the number of arguments that must be passed to * this function. */ override val arity: Int } http://bit.ly/keep-bigarity

26. Experimental features

27. Inline Classes

28. Inline Classes inline class Username(val value: String)

29. Inline Classes inline class Username(val value: String) typealias Username =

    String

30. Inline Classes inline class Username(val value: String) inline class Password(val

    value: String)

31. Inline Classes inline class Username(val value: String) inline class Password(val

    value: String) val myName = Username("nicola") val myPassword = Password("p4ssw0rd")

32. Inline Classes inline class Username(val value: String) inline class Password(val

    value: String) val myName = Username("nicola") val myPassword = Password("p4ssw0rd") myName = myPassword

33. Inline Classes inline class Username(val value: String) inline class Password(val

    value: String) val myName = Username("nicola") val myPassword = Password("p4ssw0rd") myName = myPassword myPassword = myName

34. Inline Classes inline class Username(val value: String) inline class Password(val

    value: String) val myName = Username("nicola") val myPassword = Password("p4ssw0rd") myName = myPassword myPassword = myName myName = "MyNewName" bit.ly/keep-inlineclasses

35. Unsigned Types

36. Unsigned Types val anUnsignedInteger : UInt val anUnsignedLong : ULong

    val anUnsignedByte : UByte val anUnsignedShort : UShort

37. Unsigned Types val anUnsignedInteger : UInt = 0xFFFF_FFFFu val anUnsignedLong

    : ULong = 10uL val anUnsignedByte : UByte = 0xFFu val anUnsignedShort : UShort = 0xFFFFu

38. Unsigned Types @SinceKotlin("1.3") @ExperimentalUnsignedTypes public inline class UInt internal constructor(private

    val data: Int) : Comparable<UInt> { bit.ly/keep-utype

39. Result

40. Result /** * A discriminated union that encapsulates successful outcome

    * with a value of type [T] or a failure with an arbitrary * [Throwable] exception. */ inline class Result<out T> internal constructor( internal val value: Any? // internal value -- either T or Failure ) { internal class Failure(val exception: Throwable) //... }

41. Result /** * A discriminated union that encapsulates successful outcome

    * with a value of type [T] or a failure with an arbitrary * [Throwable] exception. */ inline class Result<out T> internal constructor( internal val value: Any? // internal value -- either T or Failure ) { internal class Failure(val exception: Throwable) //... }

42. Result /** * A discriminated union that encapsulates successful outcome

    * with a value of type [T] or a failure with an arbitrary * [Throwable] exception. */ inline class Result<out T> internal constructor( internal val value: Any? // internal value -- either T or Failure ) { internal class Failure(val exception: Throwable) //... }

43. Result /** * A discriminated union that encapsulates successful outcome

    * with a value of type [T] or a failure with an arbitrary * [Throwable] exception. */ inline class Result<out T> internal constructor( internal val value: Any? // internal value -- either T or Failure ) { internal class Failure(val exception: Throwable) //... } inline fun <R> runCatching(block: () -> R): Result<R>

44. Result /** * A discriminated union that encapsulates successful outcome

    * with a value of type [T] or a failure with an arbitrary * [Throwable] exception. */ inline class Result<out T> internal constructor( internal val value: Any? // internal value -- either T or Failure ) { internal class Failure(val exception: Throwable) //... } inline fun <R> runCatching(block: () -> R): Result<R>

45. Result inline fun <R> runCatching(block: () -> R): Result<R> {

    return try { Result.success(block()) } catch (e: Throwable) { Result.failure(e) } }

46. Result fun findUserByName(name: String): ?

47. Result fun findUserByName(name: String): Result<User> Not really…

48. Result fun findUserByName(name: String): User

49. Result sealed class FindUserResult { data class Found(val user: User)

    : FindUserResult() data class NotFound(val name: String) : FindUserResult() data class MalformedName(val name: String) : FindUserResult() // other cases that need different business-specific handling code } fun findUserByName(name: String): FindUserResult

50. Result fun findUserByName(name: String): User

51. Result fun findUserByName(name: String): User val result = runCatching {

    findUserByName("...") }

52. Result - API

53. Result - Use Cases

54. Result - Use Cases try { val data = doSomething()

    processData(data) } catch(e: Throwable) { showErrorDialog(e) }

55. Result - Use Cases try { val data = doSomething()

    processData(data) } catch(e: Throwable) { showErrorDialog(e) } runCatching { doSomething() } .onFailure { showErrorDialog(it) } .onSuccess { processData(it) }

56. Result - Use Cases

57. Result - Use Cases /** * Interface representing a continuation

    after a suspension point that * returns value of type `T`. */ @SinceKotlin("1.3") public interface Continuation<in T> { /** * Context of the coroutine that corresponds to this continuation. */ public val context: CoroutineContext /** * Resumes the execution of the corresponding coroutine passing successful or failed [result] as the * return value of the last suspension point. */ public fun resumeWith(result: Result<T>) } bit.ly/keep-result

58. The Problem

59. The Problem @Test fun testMyTokenLength() { }

60. The Problem @Test fun testMyTokenLength() { val token : String?

    = getMyToken(); }

61. The Problem @Test fun testMyTokenLength() { val token : String?

    = getMyToken(); assertNotNull(token) }

62. The Problem @Test fun testMyTokenLength() { val token : String?

    = getMyToken(); assertNotNull(token) assertEquals(42, token.length) } Error(5, 22): Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type String?

63. The Problem @Test fun testMyTokenLength() { val token : String?

    = getMyToken(); assertNotNull(token) assertEquals(42, token?.length) }

64. Kotlin Contracts • The Compiler is not smart enough to


    understand the context • You know something that the compiler doesn’t know • We can provide this extra knowledge with a Kotlin Contract • The goal is to write better/cleaner code

65. Syntax

66. Syntax fun Int?.isValid(): Boolean { return this != null &&

    this != 0 }

67. Syntax fun Int?.isValid(): Boolean { contract { } return this

    != null && this != 0 }

68. Syntax fun Int?.isValid(): Boolean { contract { // Place your

    effects here } return this != null && this != 0 }

69. Effects fun isValid(number: Int?) : Boolean Int? Boolean Effect1, Effect2,

    Effect3

70. Returns fun returns(): SimpleEffect fun returns(value: Any?): SimpleEffect fun returnsNotNull():

    SimpleEffect interface SimpleEffect : Effect { infix fun implies(boolExpr: Boolean): ConditionalEffect } ConditionalEffect

71. Syntax fun Int?.isValid(): Boolean { contract { } return this

    != null && this != 0 }

72. Syntax fun Int?.isValid(): Boolean { contract { returns(true) } return

    this != null && this != 0 }

73. Syntax fun Int?.isValid(): Boolean { contract { returns(true) implies }

    return this != null && this != 0 }

74. Syntax fun Int?.isValid(): Boolean { contract { returns(true) implies (this@isValid

    != null) } return this != null && this != 0 }

75. Syntax val aInt : Int? = getAnInt() if (aInt.isValid()){ }

    else { }

76. Syntax val aInt : Int? = getAnInt() if (aInt.isValid()){ //

    Here the compiler knows that `aInt` is not nullable // thanks to the contract on `isValid` aInt.absoluteValue } else { }

77. Syntax val aInt : Int? = getAnInt() if (aInt.isValid()){ //

    Here the compiler knows that `aInt` is not nullable // thanks to the contract on `isValid` aInt.absoluteValue } else { // Here the compiler has no extra information since // the `isValid` has only a `returns(true)` effect aInt?.absoluteValue }

78. The Problem @Test fun testMyTokenLenght() { val token : String?

    = getMyToken(); assertNotNull(token) assertEquals(42, token?.length) }

79. The Problem @Test fun testMyTokenLenght() { val token : String?

    = getMyToken(); assertNotNull(token) assertEquals(42, token.length) }

80. The Problem fun assertNotNull(actual: Any?) { }

81. The Problem fun assertNotNull(actual: Any?) { org.junit.Assert.assertNotNull(actual) }

82. The Problem fun assertNotNull(actual: Any?) { contract { returns() implies

    (actual != null) } org.junit.Assert.assertNotNull(actual) }

83. CallsInPlace • lambda will not be called after the call

    to owner-function is finished. • lambda will not be passed to another function that 
 doesn’t have a similar contract. • lambda will be called the specified amount of times (kind) fun <R> callsInPlace( lambda: Function<R>, kind: InvocationKind = InvocationKind.UNKNOWN ): CallsInPlace

84. CallsInPlace InvocationKind.UNKNOWN

85. CallsInPlace InvocationKind.UNKNOWN InvocationKind.AT_MOST_ONCE

86. CallsInPlace InvocationKind.UNKNOWN InvocationKind.AT_MOST_ONCE InvocationKind.AT_LEAST_ONCE

87. CallsInPlace InvocationKind.UNKNOWN InvocationKind.AT_MOST_ONCE InvocationKind.AT_LEAST_ONCE InvocationKind.EXACTLY_ONCE

88. CallsInPlace fun main(){ val x : Int? run { x

    = 10 } println(x) }

89. CallsInPlace fun main(){ val x : Int? run { x

    = 10 } println(x) } Error:(6, 18) Variable ‘x’ must be initialized Error:(4, 8) Captured values initialization is forbidden due to possible reassignment

90. CallsInPlace public inline fun <T, R> T.run(block: T.() -> R):

    R { return block() }

91. CallsInPlace public inline fun <T, R> T.run(block: T.() -> R):

    R { contract { } return block() }

92. CallsInPlace public inline fun <T, R> T.run(block: T.() -> R):

    R { contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) } return block() }

93. CallsInPlace fun main(){ val x : Int? run { x

    = 10 } println(x) }

94. Limitations • They are not verified. 
 You’re responsible for

    writing correct contracts. • returns(value) and implies allowed values are limited • Only to top-level and block functions.

95. To infinity… • Collections Literals • SAM Conversion • Truly

    Immutability val list = listOf("1", "2", "3") val list = ["1", "2", "3"] val map = mapOf("1" to 1, "2" to 2, "3" to 3) val map = ["1" = 1, "2" = 2, "3" = 3] interface Function<T> { fun run(data: T) } val myFunction: Function<String> = { println ("data $it”) } class Foo(var v: Int) immutable class Bar(val foo: Foo) // This should fail bit.ly/kotlin-feature-survey

96. Thanks! Nicola Corti @cortinico bit.ly/ktcontracts