Kotlin's Advanced Language Features

Transcript

1. Kotlin’s Advanced Language Features

2. High Order Function's Extension

3. fun String.blowUp() { boom() } "Nooooo".blowUp()

4. fun buildString( builderAction: (StringBuilder) -> Unit ): String {a }b

   fun main(args: Array<String>) {c }e

5. fun buildString( builderAction: (StringBuilder) -> Unit ): String {a val

   sb = StringBuilder() builderAction(sb) return sb.toString() }b fun main(args: Array<String>) {c }e

6. fun buildString( builderAction: (StringBuilder) -> Unit ): String {a val

   sb = StringBuilder() builderAction(sb) return sb.toString() }b fun main(args: Array<String>) {c val s = buildString({ stringBuilder -> stringBuilder.append("Hello, ") stringBuilder.append("World!") })d }e

7. fun buildString( builderAction: (StringBuilder) -> Unit ): String {a val

   sb = StringBuilder() builderAction(sb) return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { stringBuilder -> stringBuilder.append("Hello, ") stringBuilder.append("World!") }d }e

8. fun buildString( builderAction: (StringBuilder) -> Unit ): String {a val

   sb = StringBuilder() builderAction(sb) return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { it.append("Hello, ") it.append("World!") }d }e

9. fun buildString( builderAction: (StringBuilder) -> Unit ): String {a val

   sb = StringBuilder() builderAction(sb) return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { append("Hello, ") append("World!") }d }e

10. fun buildString( builderAction: StringBuilder.() -> Unit ): String {a val

    sb = StringBuilder() builderAction(sb) return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { append("Hello, ") append("World!") }d }e

11. fun buildString( builderAction: StringBuilder.() -> Unit ): String {a val

    sb = StringBuilder() sb.builderAction() return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { append("Hello, ") append("World!") }d }e

12. fun buildString( builderAction: StringBuilder.() -> Unit ): String {a val

    sb = StringBuilder() sb.builderAction() return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { append("Hello, ") append("World!") }d }e

13. fun buildString( builderAction: StringBuilder.() -> Unit ): String {a val

    sb = StringBuilder() sb.builderAction() return sb.toString() }b fun main(args: Array<String>) {c val s = buildString { this.append("Hello, ") append("World!") }d }e
14. None

15. val taco = Taco() with(taco) { println(name) println(tasty) }

16. fun <T, R> with( receiver: T, block: T.() -> R

    ): R { return receiver.block() }

17. When do we seal the casting?

18. interface BinaryNumber object Zero : BinaryNumber object One : BinaryNumber

19. interface BinaryNumber object Zero : BinaryNumber object One : BinaryNumber

    fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 else -> throw IllegalStateException() }c }d

20. interface BinaryNumber object Zero : BinaryNumber object One : BinaryNumber

    fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 }c }d

21. interface BinaryNumber object Zero : BinaryNumber object One : BinaryNumber

    fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 else -> throw IllegalStateException() }c }d

22. interface BinaryNumber object Zero : BinaryNumber object One : BinaryNumber

    class Magic() : BinaryNumber() { fun abracadabra() { // ... } } fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 else -> throw IllegalStateException() }c }d

23. interface BinaryNumber object Zero : BinaryNumber object One : BinaryNumber

    fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 else -> throw IllegalStateException() }c }d

24. sealed class BinaryNumber object Zero : BinaryNumber() object One :

    BinaryNumber() fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 else -> throw IllegalStateException() }c }d

25. sealed class BinaryNumber object Zero : BinaryNumber() object One :

    BinaryNumber() fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 }c }d

26. sealed class BinaryNumber object Zero : BinaryNumber() object One :

    BinaryNumber() class Magic() : BinaryNumber() {z fun abracadabra() {w // ... }t }r fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 }c }d

27. sealed class BinaryNumber object Zero : BinaryNumber() object One :

    BinaryNumber() class Magic() : BinaryNumber() {z fun abracadabra() {w // ... }t }r fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 }c }d

28. sealed class BinaryNumber object Zero : BinaryNumber() object One :

    BinaryNumber() class Magic() : BinaryNumber() {z fun abracadabra() {w // ... }t }r fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 is Magic -> this.abracadabra() }c }d

29. sealed class BinaryNumber object Zero : BinaryNumber() object One :

    BinaryNumber() class Magic() : BinaryNumber() { fun abracadabra() { // ... } } fun BinaryNumber.toInt():Int {a return when (this) {b is One -> 1 is Zero -> 0 is Magic -> this.abracadabra() }c }d
30. None

31. fun requireNotNull(obj: Any?) {a if (obj == null) throw IllegalArgumentException()

    }d

32. fun requireNotNull(obj: Any?) {a if (obj == null) throw IllegalArgumentException()

    }d fun foo(s: String?) {e requireNotNull(s) s.length }f

33. fun requireNotNull(obj: Any?) {a contract { returns() implies (obj !=

    null) }c if (obj == null) throw IllegalArgumentException() }d fun foo(s: String?) {e requireNotNull(s) s.length }f
34. None

35. Error is Ever the Sequence of Haste

36. people // List<People>

37. people // List<People> .map(People::name) .filter { it.startsWith("J") }

38. people // List<People> .map(People::name) // List<People> .filter { it.startsWith("J") }

    // List<People>

39. people // List<People> .asSequence() .map(People::name) .filter { it.startsWith("J") }

40. people // List<People> .asSequence() // Sequence<People> .map(People::name) // Sequence<String> .filter

    { it.startsWith("J") } // Sequence<String>

41. people // List<People> .asSequence() // Sequence<People> .map(People::name) // Sequence<String> .filter

    { it.startsWith("J") } // Sequence<String> .toList() // List<People>

42. people .map(People::name) .find { it.startsWith("J") }

43. people .map(People::name) .find { it.startsWith("J") } And Car Jes Wil

    Pir A C J W P A C J

44. people.asSequence() .map(People::name) .find { it.startsWith("J") } And Car Jes Wil

    Pir A C J A C J
45. None

46. Generics at runtime

47. fun sumUp(items: Collection<*>) {a if (items is List<Int>) {d println(ints.sum())

    }b }c val strings: List<String> = listOf("a", "b") sumUp(strings)

48. fun sumUp(items: Collection<*>) {a if (items is List<Int>) {d println(ints.sum())

    }b }c val strings: List<String> = listOf("a", "b") sumUp(strings)

49. fun sumUp(items: Collection<*>) {a val ints = items as? List<Int>

    ?: return println("We got a list of ints") println(ints.sum()) }c val strings: List<String> = listOf("a", "b") sumUp(strings)

50. fun sumUp(items: Collection<*>) {a val ints = items as? List<Int>

    ?: return println("We got a list of ints") println(ints.sum()) }c val strings: List<String> = listOf("a", "b") sumUp(strings) ----- We got a list of ints Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Number

51. fun sumUp(items: Collection<*>) {a val ints = items as? List<Int>

    ?: return println("We got a list of ints") println(ints.sum()) }c val strings: List<String> = listOf("a", "b") sumUp(strings)

52. fun sumUp(items: Collection<Int>) {a val ints = items as? List<Int>

    ?: return println("We got a list of ints") println(ints.sum()) }c val strings: List<String> = listOf("a", "b") sumUp(strings)
53. None

54. fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>() for

    (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f

55. fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>() for

    (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f listOf("a", 1, 0x0, 2L, 'u') .filterIsInstance<String>()

56. fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>() for

    (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f listOf("a", 1, 0x0, 2L, 'u') .filterIsInstance<Int>()

57. fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>() for

    (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f listOf("a", 1, 0x0, 2L, 'u') .filterIsInstance<Char>()

58. fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>() for

    (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f
59. None

60. fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>() for

    (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f

61. inline fun <T> Iterable<*>.filterIsInstance(): List<T> {a val destination = mutableListOf<T>()

    for (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f

62. inline fun <reified T> Iterable<*>.filterIsInstance(): List val destination = mutableListOf<T>()

    for (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f

63. inline fun <reified T> Iterable<*>.filterIsInstance(): List val destination = mutableListOf<T>()

    for (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f

64. inline fun <reified T> Iterable<*>.filterIsInstance(): List val destination = mutableListOf<T>()

    for (element in this) {c if (element is T) {d destination.add(element) }p }e return destination }f listOf("a", 1, 0x0, 2L, 'u') .filterIsInstance<String>()
65. None

66. val moshi = Moshi.Builder().build() moshi.adapter(String::class.java) // JsonAdapter<String>

67. val moshi = Moshi.Builder().build() moshi.adapter(String::class.java)

68. val moshi = Moshi.Builder().build() moshi.adapter<String>()

69. inline fun <reified T> Moshi.adapter(): JsonAdapter<T> {a return this.adapter(T::class.java) }b

    val moshi = Moshi.Builder().build() moshi.adapter<String>()
70. None

71. If you really want to grow as a Klass, you've

    got to learn to delegate

72. class canTbeextended open class canbeextended

73. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    {abcdefgh }t

74. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    {abcdefgh var objectsAdded = 0 }t

75. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    {abcdefgh var objectsAdded = 0 override fun add(element: T): Boolean {w objectsAdded++ return innerSet.add(element) }p override fun addAll(c: Collection<T>): Boolean {o objectsAdded += c.size return innerSet.addAll(c) }k }t

76. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    {abcdefgh var objectsAdded = 0 override fun add(element: T): Boolean {w objectsAdded++ return innerSet.add(element) }p override fun addAll(c: Collection<T>): Boolean {o objectsAdded += c.size return innerSet.addAll(c) }k }t

77. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    {abcdefgh var objectsAdded = 0 override fun add(element: T): Boolean {w objectsAdded++ return innerSet.add(element) }p override fun addAll(c: Collection<T>): Boolean {o objectsAdded += c.size return innerSet.addAll(c) }k override val size: Int get() = innerSet.size override fun contains(element: T): Boolean { return innerSet.contains(element) } override fun containsAll(elements: Collection<T>): Boolean { return innerSet.containsAll(elements) } override fun isEmpty(): Boolean { return innerSet.isEmpty() } override fun clear() { innerSet.clear() } override fun iterator(): MutableIterator<T> { return innerSet.iterator() } override fun remove(element: T): Boolean { return innerSet.remove(element) } override fun removeAll(elements: Collection<T>): Boolean { return innerSet.removeAll(elements) } override fun retainAll(elements: Collection<T>): Boolean { return innerSet.retainAll(elements) } }t

78. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    {abcdefgh var objectsAdded = 0 override fun add(element: T): Boolean {w objectsAdded++ return innerSet.add(element) }p override fun addAll(c: Collection<T>): Boolean {o objectsAdded += c.size return innerSet.addAll(c) }k }t

79. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    by innerSet {abcdefgh var objectsAdded = 0 override fun add(element: T): Boolean {w objectsAdded++ return innerSet.add(element) }p override fun addAll(c: Collection<T>): Boolean {o objectsAdded += c.size return innerSet.addAll(c) }k }t

80. class CountingSet<T>( val innerSet: MutableCollection<T> = HashSet() ) : MutableCollection<T>

    by innerSet {abcdefgh var objectsAdded = 0 override fun add(element: T): Boolean {w objectsAdded++ return innerSet.add(element) }p override fun addAll(c: Collection<T>): Boolean {o objectsAdded += c.size return innerSet.addAll(c) }k }t
81. None

82. class Foo { val data: Int by lazy { computeStuff()

    } } • lazy • observable • vetoable • notNull

83. The Secret of Success of to Triple Your Quotes

84. """(.+)"(.+)"(.+)""".toRegex() new Regex("(.+)\"(.+)\"(.+)") "C:\\Users\\yole\\kotlin-book" """C:\Users\yole\kotlin-book""" """${'$'}99.9""" "\$99.9" "$99.9" Java Kotlin

85. assertThat(toString(taco)).isEqualTo("" + "package com.squareup.tacos\n" + "\n" + "import kotlin.String\n" +

    "\n" + "class Taco {\n" + " final override fun toString(): String = \"taco\"\n" + "}\n" + "")c

86. assertThat(toString(taco)).isEqualTo(""" package com.squareup.tacos import kotlin.String class Taco { final override

    fun toString(): String = "taco" }z """)c

87. assertThat(toString(taco)).isEqualTo(""" package com.squareup.tacos import kotlin.String class Taco { final override

    fun toString(): String = "taco" }z """)c

88. assertThat(toString(taco)).isEqualTo(""" |package com.squareup.tacos | |import kotlin.String | |class Taco {

    | final override fun toString(): String = "taco" |}z |""")c

89. assertThat(toString(taco)).isEqualTo(""" |package com.squareup.tacos | |import kotlin.String | |class Taco {

    | final override fun toString(): String = "taco" |} |""".trimMargin())c
90. None

91. And if you want these kind of dreams it's Deprecation

92. class SomeList {a fun remove(index: Int) {b }c }f

93. class SomeList {a fun remove(index: Int) {b }c fun removeAt(index:

    Int) {d }e }f

94. class SomeList {a @Deprecated("Use removeAt(index) instead.")h fun remove(index: Int) {b

    }c fun removeAt(index: Int) {d }e }f

95. class SomeList {a @Deprecated("Use removeAt(index) instead.", ReplaceWith("removeAt(index)"))h fun remove(index: Int)

    {b }c fun removeAt(index: Int) {d }e }f

96. class SomeList {a @Deprecated("Use removeAt(index) instead.", ReplaceWith("removeAt(index)"))h fun remove(index: Int)

    {b }c fun removeAt(index: Int) {d }e }f

97. Live Demo

98. None