What's New in Kotlin 1.3? - Chicago Kotlin User Group

Kotlin 1.3 is finally here and all of the new features aren't going to explain themselves. I gave this presentation to the Chicago Kotlin User Group on 2018-11-20.

Transcript

1. What’s New In
   Kotlin 1.3?
   Chicago Kotlin User Group
   2018-11-20
   Todd Ginsberg
   @ToddGinsberg
   Principal Software Developer
   

   View Slide

2. @ToddGinsberg
   Who Is This Person?
   Todd Ginsberg
   Principal Software Developer @Netspend
   (a payments company in Austin, TX)
   Chicago Java User Group Community Director and CFO
   

   View Slide

3. @ToddGinsberg
   What’s New?
   

   View Slide

4. @ToddGinsberg
   Start at the Beginning…
   fun main(args: Array) {
   }
   

   View Slide

5. @ToddGinsberg
   Start at the Beginning…
   fun main() {
   }
   

   View Slide

6. @ToddGinsberg
   Capture the Subject of When
   val answer = theAnswer()
   return when(answer) {
   42 -> "You got the right answer!"
   else -> "Sorry, $answer is not correct"
   }
   

   View Slide

7. @ToddGinsberg
   Capture the Subject of When
   when(val answer = theAnswer()) {
   42 -> "You got the right answer!"
   else -> "Sorry, $answer is not correct"
   }
   

   View Slide

8. @ToddGinsberg
   Function: associateWith()
   val people = listOf("Alice", "Bob", "Charlie")
   val nameAndLength: Map =
   people.associate { it to it.length }
   

   View Slide

9. @ToddGinsberg
   Function: associateWith()
   val people = listOf("Alice", "Bob", "Charlie")
   val nameAndLength: Map =
   people.associateWith { it.length }
   

   View Slide

10. @ToddGinsberg
    isNullOrEmpy() on Collections
    maybeEmptyArray()?.isNullOrEmpty()
    maybeEmptyMap()?.isNullOrEmpty()
    maybeEmptyCollection()?.isNullOrEmpty()
    

    View Slide

11. @ToddGinsberg
    Empty Collections and Maps
    arrayOf().ifEmpty { arrayOf(1) }
    listOf().ifEmpty { listOf(1) }
    setOf().ifEmpty { setOf(1) }
    mapOf().ifEmpty { mapOf("A" to 1) }
    

    View Slide

12. @ToddGinsberg
    Empty Sequences
    val s : Sequence? =
    maybeEmptySequence()
    

    View Slide

13. @ToddGinsberg
    Empty Sequences
    val s : Sequence =
    maybeEmptySequence()
    .orEmpty()
    

    View Slide

14. @ToddGinsberg
    Empty Sequences
    val s : Sequence =
    maybeEmptySequence()
    .orEmpty()
    .ifEmpty { someDefaultSequence() }
    

    View Slide

15. @ToddGinsberg
    Empty Strings
    val s: String =
    calculateAnswer()
    .ifEmpty { "Default" }
    

    View Slide

16. @ToddGinsberg
    Blank Strings
    val s: String =
    calculateAnswer()
    .ifEmpty { "Default" }
    .ifBlank { "Default" }
    

    View Slide

17. @ToddGinsberg
    Nullable Any HashCode
    val myHashCode: Int = myObject?.hashCode() ?: 0
    

    View Slide

18. @ToddGinsberg
    Nullable Any HashCode
    public inline fun Any?.hashCode(): Int =
    this?.hashCode() ?: 0
    val myHashCode: Int = myObject.hashCode()
    

    View Slide

19. @ToddGinsberg
    Boolean Companion
    fun Boolean.Companion.`¯＼_(ツ)_／¯`(): Boolean =
    Random.nextBoolean()
    val majorLifeDecision = Boolean.`¯＼_(ツ)_／¯`()
    

    View Slide

20. @ToddGinsberg
    Boolean Companion
    @SinceKotlin("1.3")
    companion object {}
    

    View Slide

21. @ToddGinsberg
    Basic Type Constants
    SIZE_BYTES and SIZE_BITS available on
    • Char
    • Byte
    • Short
    • Int
    • Long
    Char: 16 bits, 2 bytes
    Byte: 8 bits, 1 byte
    Short: 16 bits, 2 bytes
    Int: 32 bits, 4 bytes
    Long: 64 bits, 8 bytes
    

    View Slide

22. @ToddGinsberg
    Multiplatform random()
    import kotlin.random.*
    val random = Random.nextInt(10)
    

    View Slide

23. @ToddGinsberg
    Multiplatform random()
    public abstract class Random {
    public open fun nextInt(): Int = nextBits(32)
    companion object Default : Random() {
    // ...
    }
    }
    

    View Slide

24. @ToddGinsberg
    Multiplatform random()
    companion object Default : Random() {
    private val defaultRandom: Random =
    defaultPlatformRandom()
    override fun nextInt(): Int =
    defaultRandom.nextInt()
    }
    internal expect fun defaultPlatformRandom(): Random
    

    View Slide

25. @ToddGinsberg
    Multiplatform random()
    val winner = arrayOf(”A", ”B", ”C").random()
    val winner = listOf(”A", ”B", ”C").random()
    val letters = 'A' .. 'Z'
    val randomWord = (0..10)
    .map { letters.random() }
    .joinToString(separator = "")
    

    View Slide

26. @ToddGinsberg
    Aritiy > 22
    GOOD NEWS! We are no longer limited to 22 function arguments!
    val crazy = {
    p1: Int, p2: Int, p3: Int, p4: Int, p5: Int,
    p6: Int, p7: Int, p8: Int, p9: Int, p10: Int,
    p11: Int, p12: Int, p13: Int, p14: Int, p15: Int,
    p16: Int, p17: Int, p18: Int, p19: Int, p20: Int,
    p21: Int, p22: Int -> true
    }
    

    View Slide

27. @ToddGinsberg
    Aritiy > 22
    GOOD NEWS! We are no longer limited to 22 function arguments!
    crazy(
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
    12, 13, 14, 15, 16, 17, 18, 19, 20,
    21, 22
    )
    

    View Slide

28. @ToddGinsberg
    Aritiy > 22
    BAD NEWS – We are now limited to 254 function arguments
    val totallyReasonableThingToDo =
    { p1: Int, p2: Int, p3: Int, p4: Int, p5: Int, p6: Int, p7: Int, p8: Int, p9: Int, p10: Int,
    p11: Int, p12: Int, p13: Int, p14: Int, p15: Int, p16: Int, p17: Int, p18: Int, p19: Int, p20: Int,
    p21: Int, p22: Int, p23: Int, p24: Int, p25: Int, p26: Int, p27: Int, p28: Int, p29: Int, p30: Int,
    p31: Int, p32: Int, p33: Int, p34: Int, p35: Int, p36: Int, p37: Int, p38: Int, p39: Int, p40: Int,
    p41: Int, p42: Int, p43: Int, p44: Int, p45: Int, p46: Int, p47: Int, p48: Int, p49: Int, p50: Int,
    p51: Int, p52: Int, p53: Int, p54: Int, p55: Int, p56: Int, p57: Int, p58: Int, p59: Int, p60: Int,
    p61: Int, p62: Int, p63: Int, p64: Int, p65: Int, p66: Int, p67: Int, p68: Int, p69: Int, p70: Int,
    p71: Int, p72: Int, p73: Int, p74: Int, p75: Int, p76: Int, p77: Int, p78: Int, p79: Int, p80: Int,
    p81: Int, p82: Int, p83: Int, p84: Int, p85: Int, p86: Int, p87: Int, p88: Int, p89: Int, p90: Int,
    p91: Int, p92: Int, p93: Int, p94: Int, p95: Int, p96: Int, p97: Int, p98: Int, p99: Int, p100: Int,
    p101: Int, p102: Int, p103: Int, p104: Int, p105: Int, p106: Int, p107: Int, p108: Int, p109: Int, p110: Int,
    p111: Int, p112: Int, p113: Int, p114: Int, p115: Int, p116: Int, p117: Int, p118: Int, p119: Int, p120: Int,
    p121: Int, p122: Int, p123: Int, p124: Int, p125: Int, p126: Int, p127: Int, p128: Int, p129: Int, p130: Int,
    p131: Int, p132: Int, p133: Int, p134: Int, p135: Int, p136: Int, p137: Int, p138: Int, p139: Int, p140: Int,
    p141: Int, p142: Int, p143: Int, p144: Int, p145: Int, p146: Int, p147: Int, p148: Int, p149: Int, p150: Int,
    p151: Int, p152: Int, p153: Int, p154: Int, p155: Int, p156: Int, p157: Int, p158: Int, p159: Int, p160: Int,
    p161: Int, p162: Int, p163: Int, p164: Int, p165: Int, p166: Int, p167: Int, p168: Int, p169: Int, p170: Int,
    p171: Int, p172: Int, p173: Int, p174: Int, p175: Int, p176: Int, p177: Int, p178: Int, p179: Int, p180: Int,
    p181: Int, p182: Int, p183: Int, p184: Int, p185: Int, p186: Int, p187: Int, p188: Int, p189: Int, p190: Int,
    p191: Int, p192: Int, p193: Int, p194: Int, p195: Int, p196: Int, p197: Int, p198: Int, p199: Int, p200: Int,
    p201: Int, p202: Int, p203: Int, p204: Int, p205: Int, p206: Int, p207: Int, p208: Int, p209: Int, p210: Int,
    p211: Int, p212: Int, p213: Int, p214: Int, p215: Int, p216: Int, p217: Int, p218: Int, p219: Int, p220: Int,
    p221: Int, p222: Int, p223: Int, p224: Int, p225: Int, p226: Int, p227: Int, p228: Int, p229: Int, p230: Int,
    p231: Int, p232: Int, p233: Int, p234: Int, p235: Int, p236: Int, p237: Int, p238: Int, p239: Int, p240: Int,
    p241: Int, p242: Int, p243: Int, p244: Int, p245: Int, p246: Int, p247: Int, p248: Int, p249: Int, p250: Int,
    p251: Int, p252: Int, p253: Int, p254: Int ->
    true
    }
    

    View Slide

29. @ToddGinsberg
    Aritiy > 22
    BAD NEWS – We are now limited to 254 function arguments
    totallyReasonableThingToDo(
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
    21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,
    61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
    81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100,
    101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120,
    121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140,
    141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160,
    161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180,
    181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200,
    201, 202, 203, 204, 205, 206, 207, 208, 209, 200, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220,
    221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240,
    241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254
    )
    

    View Slide

30. @ToddGinsberg
    Aritiy > 22
    /** A function that takes 0 arguments. */
    public interface Function0 : Function
    {
    public operator fun invoke(): R
    }
    

    View Slide

31. @ToddGinsberg
    Aritiy > 22
    /** A function that takes 1 argument. */
    public interface Function1 : Function
    {
    public operator fun invoke(p1: P1): R
    }
    

    View Slide

32. @ToddGinsberg
    Aritiy > 22
    interface FunctionN : Function {
    operator fun invoke(vararg args: Any?): R
    override val arity: Int
    }
    

    View Slide

33. @ToddGinsberg
    Sealed Class Reflection
    sealed class Expr
    data class Const(val number: Double) : Expr()
    data class Sum(val e1: Expr, val e2: Expr) : Expr()
    object NotANumber : Expr()
    println(Expr::class
    .sealedSubclasses
    .map { it.simpleName }
    )
    // [Const, Sum, NotANumber]
    

    View Slide

34. @ToddGinsberg
    Nested Declarations in Annotations
    annotation class AsyncWork(
    val threads: Int = maxThreads
    ) {
    companion object {
    const val maxThreads: Int = 8
    }
    }
    

    View Slide

35. @ToddGinsberg
    Nested Declarations in Annotations
    annotation class Transaction(
    val isolation: Isolation
    ) {
    enum class Isolation {
    CREATE_NEW,
    REUSE_EXISTING, NONE
    }
    }
    @Transaction(Transaction.Isolation.CREATE_NEW)
    class Example
    

    View Slide

36. @ToddGinsberg
    Nested Declarations in Annotations
    annotation class Settings {
    annotation class Name(val name: String)
    annotation class PasswordStrategy(
    val minChars: Int,
    val minComplexity: Double = 1.0
    )
    }
    @Settings.Name("Some kind of provider")
    @Settings.PasswordStrategy(minChars = 10)
    class Provider
    

    View Slide

37. @ToddGinsberg
    Progressive Mode
    • Compiler Arguments:
    • -progressive
    • -Xprogressive
    • Trade-offs:
    • Bug fixes now
    • Possibly broken code
    

    View Slide

38. @ToddGinsberg
    Compiler Arguments
    • Compiler Arguments in a File
    • Existing: -Xargfile=filename.txt
    • New: @filename.txt
    

    View Slide

39. @ToddGinsberg
    Graduated
    

    View Slide

40. @ToddGinsberg
    Start at the Beginning…
    suspend fun main(args: Array) {
    }
    

    View Slide

41. @ToddGinsberg
    Start at the Beginning…
    suspend fun main() {
    }
    

    View Slide

42. @ToddGinsberg
    Coroutines!
    suspend fun doSomeWork(): Int {
    val a1 = async { doSomeLongRunningWork(42) }
    val a2 = async { doSomeLongRunningWork(806) }
    return a1.await() + a2.await()
    }
    

    View Slide

43. @ToddGinsberg
    Coroutines!
    suspend fun doSomeWork(): Int {
    val a1 = async { doSomeLongRunningWork(42) }
    val a2 = async { doSomeLongRunningWork(806) }
    return a1.await() + a2.await()
    }
    

    View Slide

44. @ToddGinsberg
    Structured Concurrency
    suspend fun doSomeWork(): Int =
    coroutineScope {
    val a1 = async { doSomeLongRunningWork(42) }
    val a2 = async { doSomeLongRunningWork(806) }
    a1.await() + a2.await()
    }
    

    View Slide

45. @ToddGinsberg
    Structured Concurrency
    GlobalScope.launch {
    doSomeWork()
    }
    

    View Slide

46. @ToddGinsberg
    Changes to Lazy Sequences
    fun lazyFib(): Sequence = buildSequence {
    var state = Pair(0, 1)
    while(true) {
    yield(state.second)
    state = Pair(
    state.second, state.first + state.second
    )
    }
    }
    

    View Slide

47. @ToddGinsberg
    Changes to Lazy Sequences
    fun lazyFib(): Sequence = sequence {
    var state = Pair(0, 1)
    while(true) {
    yield(state.second)
    state = Pair(
    state.second, state.first + state.second
    )
    }
    }
    

    View Slide

48. @ToddGinsberg
    Experimental
    

    View Slide

49. @ToddGinsberg
    Inline Classes
    fun canVote(years: Int): Boolean =
    years >= 18
    inline class Age(val years: Int)
    fun canVote(age: Age): Boolean =
    age.years >= 18
    

    View Slide

50. @ToddGinsberg
    Inline Classes
    inline class Age(val years: Int) {
    fun minor(): Boolean = years < 18
    }
    fun canVote(age: Age): Boolean =
    !age.minor()
    

    View Slide

51. @ToddGinsberg
    Inline Classes
    • Must have a public constructor with a single val
    • No init block
    • Must be final
    • Cannot extend anything
    • Cannot have any additional properties
    • Must be a top level class
    • Cannot have inner classes
    • Cannot be defined with recursively defined generics
    Limitations!
    

    View Slide

52. @ToddGinsberg
    Unsigned Types
    val aUInt: UInt = 42u
    val aULong: ULong = 42uL
    

    View Slide

53. @ToddGinsberg
    Unsigned Types
    val myUByte: UByte = someByte.toUByte()
    val myUShort: UShort = someShort.toUShort()
    val myUInt: UInt = someInt.toUInt()
    val myULong: ULong = someLong.toULong()
    

    View Slide

54. @ToddGinsberg
    Unsigned Types
    val uByte: UByte = "255".toUByte()
    val uShort: UShort = "65535".toUShort()
    val uInt: UInt = "4294967295".toUInt()
    val uLong: ULong = "18446744073709551615".toULong()
    

    View Slide

55. @ToddGinsberg
    Unsigned Types
    As well as…
    • Hex Literals = 0xFFFF_FFFFu
    • Unsigned Arrays = uintArrayOf(1u, 2u, 3u)
    • Unsigned Ranges = (0u .. UInt.MAX_VALUE)
    • Remove warnings with @ExperimentalUnsignedTypes
    

    View Slide

56. @ToddGinsberg
    Contracts
    fun CharSequence?.isNullOrBlank() : Boolean =
    this == null || this.isBlank()
    val s: String? = calculateString()
    if(!s.isNullOrBlank()) {
    s?.reversed()
    }
    

    View Slide

57. @ToddGinsberg
    Contracts
    @ExperimentalContracts
    fun CharSequence?.isNullOrBlank() : Boolean {
    contract {
    returns (false) implies
    (this@isNullOrBlank != null)
    }
    return this == null || this.isBlank()
    }
    

    View Slide

58. @ToddGinsberg
    Contracts
    @ExperimentalContracts
    fun main(args: Array) {
    val s: String? = calculateString()
    if(!s.isNullOrBlank()) {
    s.reversed()
    }
    }
    

    View Slide

59. @ToddGinsberg
    Contracts
    fun main(args: Array) {
    val myValue: String
    run {
    myValue = "Hello, World!”
    }
    }
    

    View Slide

60. @ToddGinsberg
    Contracts
    @ExperimentalContracts
    inline fun run(block: () -> R): R {
    contract {
    callsInPlace(
    block,
    InvocationKind.EXACTLY_ONCE
    )
    }
    return block()
    }
    

    View Slide

61. @ToddGinsberg
    Experimental Annotations
    @Experimental(level = Experimental.Level.WARNING)
    annotation class MyExperimentalApi
    @MyExperimentalApi
    class SomeExperimentalThing {
    // ...
    }
    

    View Slide

62. @ToddGinsberg
    Experimental Annotations
    @MyExperimentalApi
    fun doSomething(n: SomeExperimentalThing) {
    // ...
    }
    @UseExperimental(MyExperimentalApi::class)
    fun doSomethingElse() {
    SomeExperimentalThing().doSomething()
    }
    

    View Slide

63. @ToddGinsberg
    More Details
    https://todd.ginsberg.com/post/kotlin-1.3-features/
    

    View Slide

64. Than You!
    @ToddGinsberg
    https://todd.ginsberg.com
    todd@ginsberg.com
    

    View Slide