2017_12_18-19_Kotlin_Conf_Report_Kotlin_Types_Updated

CA.kt #5, 6 Kotlin Conf Report in Osaka, Fukuoka
Kotlin Types
This presentation based on Kotlin Exposed Type by Svetlana Isakova in Kotlin Conf 2017.

https://cyberagent.connpass.com/event/73540/
https://cyberagent.connpass.com/event/73541/

Transcript

1. Kotlin Conf報告会 @ CA.kt #5, 6 AAkira - Kotlin Types -
2. @_a_akira AAkira CyberAgent, Inc. Akira Aratani private lateinit var aakira : User data class User(val name: String, val twitterId: String, val githubId: String, val company: String) print("Name : ${aakira.name}”) println("Github Id : ${aakira.githubId}") print("Twitter Id : ${aakira.twitterId}") println("Company : ${aakira.company}") $ whois
3. About • 生放送配信プラットフォーム　≠ AbemaTV　≒ • M11の頃からFull Kotlinで開発 • サーバサイドも1年前からKotlinを使用
4. 私とKotlin M1 2012-04-12 M11 2015-03-19 M14 2015-10-01 1.0-beta4 2015-12-22 M13 2015-09-16 1.0 2016-02-16 1.0-RC 2016-02-04 2016-01-21 Release 2015-04 開発開始 kotlin FRESH 1.1 2017-03-01 2017-05-15 Renewal
7. Svetlana Isakova @JetBrains Kotlin in Action の著者の1人
9. Agenda • Basic types • Nullable types • Collection types
10. Agenda • Basic types • Nullable types • Collection types • Kotlin/Java types • Any, Unit, Nothing, void • Collections →
11. Kotlin types Java types
12. Kotlin, Java Types fun foo(): Int = 1 fun bar(): Int? = 1
13. Kotlin, Java Types
14. Kotlin, Java Types public static final int foo() { return 1; } @Nullable public static final Integer bar() { return Integer.valueOf(1); }
15. Kotlin, Java Types public static final int foo() { return 1; } @Nullable public static final Integer bar() { return Integer.valueOf(1); }
16. Kotlin, Java Types Int → int Int? → java.lang.Integer
17. Kotlin, Java Types Double → double Double? → java.lang.Double Boolean → boolean Boolean? → java.lang.Boolean
18. Kotlin, Java Types List<Int> → java.util.List<Integer> kotlin.String → java.lang.String Array<Int> → Integer[]
19. Kotlin, Java Types List<Int> → java.util.List<Integer> kotlin.String → java.lang.String Array<Int> → Integer[]
20. Kotlin, Java Types "one.two.".replaceAll(".", "*")
21. Kotlin, Java Types "one.two.".replaceAll(".", "*") ********
22. Kotlin, Java Types "one.two.".replaceAll(".", "*") "one.two.".replace(".", "*") ********
23. Kotlin, Java Types "one.two.".replaceAll(".", "*") "one.two.".replace(".", "*") ******** one*two*
24. Kotlin, Java Types "one.two.".replace(".".toRegex(), "*") "one.two.".replaceAll(".", "*") "one.two.".replace(".", "*") ******** one*two*
25. Any, Unit, Nothing, void
26. Any java.lang.Object Any, Unit, Nothing, void
27. Any, Unit, Nothing, void The root of the Kotlin class hierarchy. Every Kotlin class has [Any] as a superclass. Any
28. Any, Unit, Nothing, void log(2017) fun log(any: Any) { println("Value: $any") } fun log(i: Int) { println("Value: $i”) }
29. Any, Unit, Nothing, void log(2017) fun log(any: Any) { println("Value: $any") } fun log(i: Int) { println("Value: $i”) } Auto boxing
30. Any, Unit, Nothing, void fun log(i: Int) { println("Value: $i”) }
31. Any, Unit, Nothing, void fun log(any: Any) { println("Value: $any") }
32. Any, Unit, Nothing, void Int String Any
33. val hoge: Int? = 2017 log(hoge) fun log(any: Any) { println("Value: $any") } Any, Unit, Nothing, void
34. val hoge: Int? = 2017 log(hoge) fun log(any: Any) { println("Value: $any") } Any, Unit, Nothing, void ⇨ Compile Error
35. Any, Unit, Nothing, void Any Nullable Type Any? Non-null Type
36. Any, Unit, Nothing, void void Unit Nothing
37. Any, Unit, Nothing, void void Unit Nothing ≠ ,
38. Any, Unit, Nothing, void void Unit
39. Any, Unit, Nothing, void Unit The type with only one value: the Unit object. This type corresponds to the `void` type in Java.
40. Any, Unit, Nothing, void void Unit ⇨ 意味のない値を返す =
41. Any, Unit, Nothing, void Nothing has no instances. You can use Nothing to represent "a value that never exists”: for example, if a function has the return type of Nothing,
 it means that it never returns (always throws an exception). Nothing
42. Any, Unit, Nothing, void Nothing ⇨ 存在しないを表す, 値は返さない
43. Any, Unit, Nothing, void val foo = if (bar) { 123 } else { fail() } fun fail() { throw IllegalStateException() }
44. Any, Unit, Nothing, void val foo = if (bar) { 123 } else { fail() } fun fail(): Unit { throw IllegalStateException() }
45. Any, Unit, Nothing, void val foo = if (bar) { 123 } else { fail() } fun fail(): Unit { throw IllegalStateException() }
46. Any, Unit, Nothing, void val foo = if (bar) { 123 } else { fail() } fun fail(): Unit { throw IllegalStateException() } Int Unit
47. Any, Unit, Nothing, void Int Unit Any
48. Any, Unit, Nothing, void val foo: Any = if (bar) { 123 } else { fail() } fun fail(): Unit { throw IllegalStateException() }
49. Any, Unit, Nothing, void val foo: Any = if (bar) { 123 } else { fail() } fun fail(): Unit { throw IllegalStateException() } ⇨ fooはInt型にしたい
50. Any, Unit, Nothing, void val foo = if (bar) { 123 } else { fail() } fun fail(): Nothing { throw IllegalStateException() }
51. Any, Unit, Nothing, void val foo = if (bar) { 123 } else { fail() } fun fail(): Nothing { throw IllegalStateException() } Int Nothing
52. Any, Unit, Nothing, void Int Unit Any Nothing
53. Any, Unit, Nothing, void val foo: Int = if (bar) { 123 } else { fail() } fun fail(): Nothing { throw IllegalStateException() }
54. Any, Unit, Nothing, void val foo: Int = if (bar) { 123 } else { fail() } fun fail(): Nothing { throw IllegalStateException() }
55. Nothing? Any, Unit, Nothing, void
56. Any, Unit, Nothing, void Int Unit Any Nothing
57. Any, Unit, Nothing, void Non-null Type Any Nothing Non-null Type
58. Any, Unit, Nothing, void Any Any? Non-null Type Nothing
59. Any, Unit, Nothing, void Any Nullable Type Any? Non-null Type Nothing
60. Any, Unit, Nothing, void Any Nullable Type Any? Non-null Type Nothing? Nothing
61. Collections
62. Collections kotlin.MutableList kotlin.List
63. Collections val mutableList = mutableListOf(1, 2, 3) val list: List<Int> = mutableList println(list) // [1, 2, 3]
64. Collections val mutableList = mutableListOf(1, 2, 3) val list: List<Int> = mutableList println(list) // [1, 2, 3] mutableList.add(4) println(list)
65. Collections val mutableList = mutableListOf(1, 2, 3) val list: List<Int> = mutableList println(list) // [1, 2, 3] mutableList.add(4) println(list) // [1, 2, 3, 4]
66. Collections ⇨ Read-only ≠ immutable mutableList.add(4) println(list) // [1, 2, 3, 4]
67. Collections fun foo(): List<Int> = listOf(1) fun bar(): MutableList<Int> = mutableListOf(1) ⇨ Decompile
68. Collections @NotNull public static final List foo() { return CollectionsKt.listOf(Integer.valueOf(1)); } @NotNull public static final List bar() { return CollectionsKt.mutableListOf(
 new Integer[]{Integer.valueOf(1)}); }
69. Collections @NotNull public static final List foo() { return CollectionsKt.listOf(Integer.valueOf(1)); } @NotNull public static final List bar() { return CollectionsKt.mutableListOf(
 new Integer[]{Integer.valueOf(1)}); }
70. Collections kotlin.MutableList kotlin.List java.util.ArrayList
71. Summary
72. Summary • Decompile to Java code • Nothing ≠ Unit, void • Read-only ≠ immutable
73. Have a nice Kotlin!