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2017_11_14_Kotlin_Conf_Report_Kotlin_Types

AAkira
November 14, 2017

 2017_11_14_Kotlin_Conf_Report_Kotlin_Types

CA.kt #4 Kotlin Conf Report
Kotlin Types
This presentation based on Kotlin Exposed Type by Svetlana Isakova in Kotlin Conf 2017.

https://cyberagent.connpass.com/event/70423/

AAkira

November 14, 2017
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  1. @_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
  2. 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
  3. Agenda • Basic types • Nullable types • Collection types

    • Kotlin/Java types • Unit, Nothing, void • Collections →
  4. Kotlin, Java Types public static final int foo() { return

    1; } @Nullable public static final Integer bar() { return Integer.valueOf(1); }
  5. Kotlin, Java Types public static final int foo() { return

    1; } @Nullable public static final Integer bar() { return Integer.valueOf(1); }
  6. Unit, Nothing, void Unit The type with only one value:

    the Unit object. This type corresponds to the `void` type in Java.
  7. 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
  8. Unit, Nothing, void val foo = if (bar) { 123

    } else { fail() } fun fail() { throw IllegalStateException() }
  9. Unit, Nothing, void val foo = if (bar) { 123

    } else { fail() } fun fail(): Unit { throw IllegalStateException() }
  10. Unit, Nothing, void val foo = if (bar) { 123

    } else { fail() } fun fail(): Unit { throw IllegalStateException() }
  11. Unit, Nothing, void val foo = if (bar) { 123

    } else { fail() } fun fail(): Unit { throw IllegalStateException() } Int Unit
  12. Unit, Nothing, void val foo: Any = if (bar) {

    123 } else { fail() } fun fail(): Unit { throw IllegalStateException() }
  13. Unit, Nothing, void val foo: Any = if (bar) {

    123 } else { fail() } fun fail(): Unit { throw IllegalStateException() } ⇨ fooはInt型にしたい
  14. Unit, Nothing, void val foo = if (bar) { 123

    } else { fail() } fun fail(): Nothing { throw IllegalStateException() }
  15. Unit, Nothing, void val foo = if (bar) { 123

    } else { fail() } fun fail(): Nothing { throw IllegalStateException() } Int Nothing
  16. Unit, Nothing, void val foo: Int = if (bar) {

    123 } else { fail() } fun fail(): Nothing { throw IllegalStateException() }
  17. Unit, Nothing, void val foo: Int = if (bar) {

    123 } else { fail() } fun fail(): Nothing { throw IllegalStateException() }
  18. Collections val mutableList = mutableListOf(1, 2, 3) val list: List<Int>

    = mutableList println(list) // [1, 2, 3] mutableList.add(4) println(list)
  19. 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]
  20. 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)}); }
  21. 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)}); }