Kotlin ist auch eine Insel

From my talk at Code Talks 2016 (https://www.codetalks.de/):
Kotlin and some Extension Function Magic for beginners. (german)

#CodeTalksHH

Transcript

1. Lovis Möller @lovisbrot #codetalkshh KOTLIN IST AUCH EINE INSEL
2. Kotlin ist auch eine Sprache Lovis Möller @lovisbrot #codetalkshh
3. Kotlin ist auch eine Sprache • Entwickelt von JetBrains • Concise & Expressive • Sicher • Pragmatisch • 100% Interoperabel mit Java und den Java Apis • Für Java Entwickler leicht zu erlernen Lovis Möller @lovisbrot #codetalkshh
4. public class Person { private final long id;
 private String name;
 public Person(long id) { … } public Person(long id, String name) { … } public long getId() { … }
 public String getName() { … }
 public void setName(String name) { … } public boolean equals(Object o) { … } public int hashCode() { … }
 }
5. class Person (val id: Long, var name: String?)
6. data class Person (val id: Long, var name: String?)
7. data class Person (val id: Long, var name: String?) equals() hashCode() copy() toString()
8. data class Person (val id: Long, var name: String?) equals() hashCode() copy() toString() val = immutable / final
9. data class Person (val id: Long, var name: String?) equals() hashCode() copy() toString() val = immutable / final "normale" variable
10. data class Person (val id: Long, var name: String?) equals() hashCode() copy() toString() optional, d.h. null ist erlaubt "normale" variable val = immutable / final
11. data class Person (val id: Long, var name: String?) equals() hashCode() copy() toString() "normale" variable optional, d.h. null ist erlaubt val = immutable / final
12. data class Person (val id: Long, var name: String?) Konstruktoparameter werden automatisch zu properties
13. data class Person (val id: Long, var name: String?)
14. data class Person (val id: Long, var name: String?) { var age: Int = 5 fun getInfos() { return "$Name, $age Jahre alt." } }
15. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos() { return "$Name, $age Jahre alt." } }
16. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos() { return "$Name, $age Jahre alt." } }
17. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos() { return "$Name, $age Jahre alt." } } keine primitiven Typen
18. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos() { return "$Name, $age Jahre alt." } }
19. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos(): String { return "$name, $age Jahre alt." } }
20. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos(): String = "$name, $age Jahre alt." }
21. data class Person (val id: Long, var name: String? = null) { var age: Int = 5 fun getInfos() = "$name, $age Jahre alt." }
22. data class Person (val id: Long, var name: String? = null) { var age:= 5 fun getInfos() = "$name, $age Jahre alt." }
23. val person: Person = Person(1, null) val name = person?.name
24. val person: Person = Person(1) val name = person?.name
25. val person = Person(1) val name = person?.name
26. val person = Person(1) val name = person.name?.toUpperCase()
27. val person = Person(1) val name = person.name?.toUpperCase() Safe call operator
28. val person = Person(1) val name = person.name?.toUpperCase() Safe call operator Abgeleiteter Typ?
29. val person = Person(1) val name: String? = person.name?.toUpperCase() Abgeleiteter Typ.
30. QUIZ
31. if(person != null) { println(person.name) }
32. if(person != null) { println(person.name) } var person: Person? = null ...
33. if(person != null) { println(person.name) } Smart Cast, Safe Call nicht nötig var person: Person? = null ...
34. if(person != null) { println(person.name) } var person: Person? = null ...
35. person?.let ({ p -> println(p.name) }) var person: Person? = null ...
36. person?.let ({ p -> println(p.name) }) var person: Person? = null ...
37. person?.let ({ p -> println(p.name) }) var person: Person? = null ...
38. person?.let ({ println(it.name) }) var person: Person? = null ...
39. person?.let { println(it.name) } var person: Person? = null ...
40. public inline fun <T, R> T.let(block: (T) -> R): R = block(this)
41. public inline fun <T, R> T.let(block: (T) -> R): R = block(this) Extension Funktion
42. public inline fun <T, R> T.let(block: (T) -> R): R = block(this) Extension Funktion Parameter ist Funktion -> Higher order Function
43. public inline fun <T, R> T.let(block: (T) -> R): R = block(this) Extension Funktion Parameter ist Funktion -> Higher order Function Zugriff auf "this"
44. public class Util { private Util() {} public static<T,R> R let(T receiver, Function<T,R> block) { return block.apply(receiver); } }
45. public inline fun <T, R> T.let(block: (T) -> R): R = block(this)
46. public inline fun <T, R> T.let(block: (T) -> R): R = block(this) person.let { println(it.name) }
47. public inline fun <T, R> T.let(block: (T) -> R): R = block(this) person.let { println(it.name) } Util.let(person, new Function<Person, Void>() { System.out.println(person.name); }); vs
48. val person = Person(1, "Jack Bauer").apply { age = 50 }
49. val textView = TextView(context).apply { text = "Moin" ellipsize = TruncateAt.MARQUEE textColor = R.color.white }
50. fun ImageView.setImageUrl(url: String) { Picasso.with(context).load(url).into(imageView) }
51. fun ImageView.setImageUrl(url: String) { Picasso.with(context).load(url).into(this) }
52. fun ImageView.setImageUrl(url: String) { Picasso.with(context).load(url).into(this) } imageView.setImageUrl("http://...")
53. var TextView.drawableLeft: Drawable?
 get() = compoundDrawables[0]
 set(left) {
 setCompoundDrawablesWithIntrinsicBounds(left, compoundDrawables[1], compoundDrawables[2], compoundDrawables[3])
 }
54. var TextView.drawableLeft: Drawable?
 get() = compoundDrawables[0]
 set(left) {
 setCompoundDrawablesWithIntrinsicBounds(left, compoundDrawables[1], compoundDrawables[2], compoundDrawables[3])
 }
55. var TextView.drawableLeft: Drawable?
 get() = compoundDrawables[0] //getCompundDrawables()[0]
 set(left) {
 setCompoundDrawablesWithIntrinsicBounds(left, compoundDrawables[1], compoundDrawables[2], compoundDrawables[3])
 }
56. var TextView.drawableLeft: Drawable?
 get() = compoundDrawables[0]
 set(left) {
 setCompoundDrawablesWithIntrinsicBounds(left, compoundDrawables[1], compoundDrawables[2], compoundDrawables[3])
 }
57. var TextView.drawableLeft: Drawable?
 get() = compoundDrawables[0]
 set(left) {
 setCompoundDrawablesWithIntrinsicBounds(left, compoundDrawables[1], compoundDrawables[2], compoundDrawables[3])
 } textView.drawableLeft = getDrawable(R.id.lightBulb) // set val left = textView.drawableLeft // get
58. fun createHtml() = html { head { title {+"Typesafe builders with Kotlin"} } body { h1 {+"Typesafe builders with Kotlin"} p {+"this format can be used as an alternative markup to XML"} } }
59. fun createHtml() = html { head { title {+"Typesafe builders with Kotlin"} } body { h1 {+"Typesafe builders with Kotlin"} p {+"this format can be used as an alternative markup to XML"} } } fun html(init: HTML.() -> Unit): HTML { val html = HTML() html.init() return html }
60. fun createHtml() = html { head { title {+"Typesafe builders with Kotlin"} } body { h1 {+"Typesafe builders with Kotlin"} p {+"this format can be used as an alternative markup to XML"} } } fun html(init: HTML.() -> Unit): HTML { val html = HTML() html.init() return html } Extension function fun html(init: HTML.() -> Unit): HTML {
61. fun createHtml() = html { head { title {+"Typesafe builders with Kotlin"} } body { h1 {+"Typesafe builders with Kotlin"} p {+"this format can be used as an alternative markup to XML"} } } fun html(init: HTML.() -> Unit): HTML { val html = HTML() html.init() return html } fun html(init: HTML.() -> Unit): HTML {
62. fun createHtml() = html { head { title {+"Typesafe builders with Kotlin"} } body { h1 {+"Typesafe builders with Kotlin"} p {+"this format can be used as an alternative markup to XML"} } } fun html(init: HTML.() -> Unit): HTML { val html = HTML() html.init() return html } fun html(init: HTML.() -> Unit): HTML { Funktionen der Klasse HTML
63. fun html(init: HTML.() -> Unit): HTML { val html = HTML() html.init() return html } fun html(init: HTML.() -> Unit): HTML { fun createHtml() = html { head { title {+"Typesafe builders with Kotlin"} } body { h1 {+"Typesafe builders with Kotlin"} p {+"this format can be used as an alternative markup to XML"} } }
64. verticalLayout { padding = dip(30) editText { hint = "Name" textSize = 24f } editText { hint = "Password" textColor = Color.BLUE } button("Login") { onClick { ... } } }
65. verticalLayout { padding = dip(30) editText { hint = "Name" textSize = 24f } editText { hint = "Password" textColor = Color.BLUE } button("Login") { onClick { ... } } } ANKO github.com/Kotlin/anko
66. apply { plugin<AppPlugin>() plugin<KotlinAndroidPluginWrapper>() } android { buildToolsVersion("24.0.2") compileSdkVersion(24) defaultConfigExtension { setMinSdkVersion(21) setTargetSdkVersion(23) applicationId = "com.example.kotlingradle" versionCode = 1 versionName = "1.0-RC" } … } dependencies { … }
67. apply { plugin<AppPlugin>() plugin<KotlinAndroidPluginWrapper>() } android { buildToolsVersion("24.0.2") compileSdkVersion(24) defaultConfigExtension { setMinSdkVersion(21) setTargetSdkVersion(23) applicationId = "com.example.kotlingradle" versionCode = 1 versionName = "1.0-RC" } … } dependencies { … } GRADLE gradle.org/blog/kotlin-meets-gradle/
68. val items = listOf("CODE", "TALKS", null, "2016") items.filterNonNull() .map { text -> text.toLowerCase() }.reduce { a,b -> "$a.$b" }.let { println(it) } //prints code.talks.2016
69. val items = listOf("CODE", "TALKS", null, "2016") items.filterNonNull() .map { text -> text.toLowerCase() }.reduce { a,b -> "$a.$b" }.let { println(it) } //prints code.talks.2016
70. val items = listOf("CODE", "TALKS", null, "2016") items.filterNonNull() .map { text -> text.toLowerCase() }.reduce { a,b -> "$a.$b" }.let { println(it) } //prints code.talks.2016
71. val items = listOf("CODE", "TALKS", null, "2016") items.filterNonNull() .map { text -> text.toLowerCase() }.reduce { a,b -> "$a.$b" }.let { println(it) } //prints code.talks.2016
72. val items = listOf("CODE", "TALKS", null, "2016") items.filterNonNull() .map { text -> text.toLowerCase() }.reduce { a,b -> "$a.$b" }.let { println(it) } //prints code.talks.2016
73. val items = listOf("CODE", "TALKS", null, "2016") items.filterNonNull() .map { text -> text.toLowerCase() }.reduce { a,b -> "$a.$b" }.let { println(it) } //prints code.talks.2016
74. val immutableList = listOf("Code", "Talks", "2016")
75. val immutableList = listOf("Code", "Talks", "2016") erzeugt eine immutable List
76. val immutableList = listOf("Code", "Talks", "2016")
77. val mutableList = mutableListOf("Code", "Talks", "2016")
78. val mutableList = arrayListOf("Code", "Talks", "2016")
79. https://blog.jetbrains.com/kotlin/2012/09/kotlin-m3-is-out/
80. https://blog.jetbrains.com/kotlin/2012/09/kotlin-m3-is-out/
81. https://blog.jetbrains.com/kotlin/2012/09/kotlin-m3-is-out/
82. https://blog.jetbrains.com/kotlin/2012/09/kotlin-m3-is-out/
83. Ready for production?
84. Ready for production?
85. • kotlinlang.org • try.kotlinlang.org • leanpub.com/kotlin-for-android-developers Lovis Möller @lovisbrot #codetalkshh
86. println("Thanks a lot!") Lovis Möller @lovisbrot #codetalkshh