Let Kotlin Come To You

Kotlin is a statically typed, multi-platform language, developed by JetBrains. It’s use has increased dramatically in the past year. What does the language offer us, and why might we choose it? In this talk we’ll go over some of the basics of Kotlin, the benefits, and how we can use it in our day to day development. You will walk away from this talk with the tools you need to get started learning and building with Kotlin, whether you’re working with the JVM, JavaScript, or native.

Transcript

1. LET KOTLIN COME TO YOU
   VICTORIA GONDA
   VICTORIAGONDA.COM
   

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2. @TTGonda
   WHO AM I?
   ▸ Android Engineer at Buffer
   ▸ Author at Ray Wenderlich
   ▸ Chicago
   ▸ Dancer
   

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3. @TTGonda
   

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4. “STATICALLY TYPED PROGRAMMING
   LANGUAGE FOR MODERN
   MULTIPLATFORM APPLICATIONS”
   kotlinlang.org
   

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5. @TTGonda
   KOTLIN
   ▸ Developed by JetBrains
   ▸ Available for JVM, Android, JavaScript, and Native
   ▸ Concise, safe interoperable, tool-friendly
   ▸ Built in IDE support (with JetBrains products)
   

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6. @TTGonda
   KOTLIN
   ▸ Strong, static, inferred, null safe typing
   ▸ Immutability by default
   ▸ Smart casting
   ▸ Higher order functions
   ▸ Boilerplate reduction
   

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7. TYPING
   

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8. @TTGonda
   STATICALLY TYPED
   final String name = "Victoria";
   val name = "Victoria"
   

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9. @TTGonda
   NULL TYPING
   val icecream: IceCream?
   

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10. @TTGonda
    icecream.flavor
    

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11. @TTGonda
    if (icecream != null) {
    return icecream.flavor
    } else {
    return null
    }
    

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12. @TTGonda
    SAFE CALL OPERATOR
    return icecream?.flavor
    

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13. @TTGonda
    !! OPERATOR
    return icecream!!.flavor
    

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14. @TTGonda
    ELVIS OPERATOR
    return icecream?.flavor ?: "Chocolate Chip"
    

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15. @TTGonda
    NULL SAFE SCOPING WITH HIGHER ORDER FUNCTIONS
    return icecream?.let({ nonNullIceCream ->

    nonNullIceCream.flavor })

    return icecream?.let({ it.flavor })

    return icecream?.let { it.flavor }

    return icecream?.let(IceCream::flavor)
    

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16. IMMUTABILITY
    

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17. @TTGonda
    val conference = "GOTO Chicago"
    conference = "GOTO Chicago 2018”
    

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18. @TTGonda
    var conference = "GOTO Chicago"
    conference = "GOTO Chicago 2018”
    

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19. @TTGonda
    val readOnlylist = listOf(1, 2, 3)
    val mutableList = mutableListOf("a", "b", “c")
    

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20. SMART CASTING
    

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21. @TTGonda
    SMART CASTING
    class Conference(val year: String): Event()
    fun smartCasting(event: Event) {
    if (event is Conference) {
    event.year
    }
    }
    

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22. BOILERPLATE
    REDUCTION
    

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23. @TTGonda
    class Cupcake(
    val flavor: String,
    var icing: String?
    )
    CLASSES
    

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24. @TTGonda
    public final class Cupcake {
    @NotNull
    private final String flavor;
    @Nullable
    private String icing;
    @NotNull
    public final String getFlavor() {}
    @Nullable
    public final String getIcing() {}
    public final void setIcing(@Nullable String var1) {}
    public Cupcake(@NotNull String flavor, @Nullable String icing) {}
    }
    

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25. @TTGonda
    data class Cupcake(
    val flavor: String,
    var icing: String?
    )
    

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26. @TTGonda
    public final class Cupcake {
    // …
    @NotNull
    public final String component1() {}
    @Nullable
    public final String component2() {}
    @NotNull
    public final Cupcake copy(@NotNull String flavor, @Nullable String icing) {}
    public String toString() {}
    public int hashCode() {}
    public boolean equals(Object var1) {}
    }
    

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27. SEALED CLASSES
    

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28. @TTGonda
    ENUMS
    enum class GetConferenceState {
    SUCCESS, ERROR, PROGRESS
    }
    

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29. @TTGonda
    SEALED CLASSES
    sealed class GetConferenceState {
    class Success(val result: Conference): GetConferenceState()
    data class Error(val errorMessage: String): GetConferenceState()
    object InProgress: GetConferenceState()
    }
    

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30. @TTGonda
    SEALED CLASSES
    when(state) {
    is GetConferenceState.Success -> showConference(state.conference)
    is GetConferenceState.Error -> showError(state.errorMessage)
    is GetConferenceState.InProgress -> showLoading()
    }
    

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31. @TTGonda
    AND MORE!
    

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32. @TTGonda
    

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33. WHERE CAN KOTLIN BE
    USED?
    

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34. @TTGonda
    WHERE CAN KOTLIN BE USED?
    ▸ JVM, Android, JavaScript, Native
    ▸ Mobile, Server, Browser, Views
    ▸ IntelliJ, Android Studio, Eclipse, Standalone Compilers
    ▸ Kotlin all the things!
    ▸ Try it out in the browser (try.kotlinlang.org)
    

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35. @TTGonda
    JAVA VIRTUAL MACHINE
    ▸ Use on the server, Android, Java applications
    ▸ Spring Boot, for example
    ▸ Anywhere the JVM lives
    ▸ Interoperable with Java
    ▸ More flexible and concise than Java
    ▸ Less feature bloat than Scala
    

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36. @TTGonda
    JVM - INTELLIJ
    

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37. @TTGonda
    JVM - INTELLIJ
    ▸ New Kotlin file in src directory
    fun main(args: Array) {
    println("Hello GOTO Chicago")
    }
    ▸ Run! ▶
    

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38. @TTGonda
    JVM - GRADLE
    ▸ Set up gradle-kotlin plugin and apply it. Add dependencies.
    repositories {
    mavenCentral()
    }
    dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib"
    }
    ▸ Alternatively in IntelliJ, Tools > Kotlin > Configure Kotlin in Project
    

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39. @TTGonda
    JVM - ECLIPSE
    ▸ Download plugin from Marketplace
    ▸ File > New > Kotlin Project
    

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40. @TTGonda
    JVM - ECLIPSE
    ▸ New Kotlin file in src directory
    fun main(args: Array) {
    println("Hello GOTO Chicago")
    }
    ▸ Run As > Kotlin Application ▶
    

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41. @TTGonda
    JVM - COMMAND LINE
    ▸ Install Kotlin
    // hello.kt
    fun main(args: Array) {
    println("Hello GOTO Chicago")
    }
    ▸ Run! ▶
    $ kotlinc hello.kt -include-runtime -d hello.jar
    $ java -jar hello.jar
    

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42. @TTGonda
    JAVA EQUIVALENT
    public final class HelloKt {
    public static final void main(@NotNull String[] args) {
    Intrinsics.checkParameterIsNotNull(args, "args");
    String var1 = "Hello GOTO Chicago";
    System.out.println(var1);
    }
    }
    

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43. @TTGonda
    CONVERTING JAVA TO KOTLIN
    ▸ Android Studio and IntelliJ have built in conversion
    ▸ Three ways to get there
    ▸ Code > Convert Java File to Kotlin File
    ▸ ⎇⇧⌘K
    ▸ Search for action “Convert File to Kotlin File
    

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44. @TTGonda
    JVM - OTHER OPTIONS
    ▸ Ant
    ▸ Maven
    ▸ Griffon
    

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45. @TTGonda
    ANDROID
    ▸ More flexible and concise than Java
    ▸ Interoperable with Java
    ▸ Can use all the same libraries
    ▸ Supported in Android Studio
    

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46. @TTGonda
    ANDROID STUDIO
    

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47. @TTGonda
    JAVASCRIPT
    ▸ Use in browser, and any JS framework
    ▸ ReactJS, for example
    ▸ Type safe
    ▸ Interop with JavaScript
    

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48. @TTGonda
    JS - INTELLIJ
    

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49. @TTGonda
    JS - INTELLIJ
    ▸ New Kotlin file in src directory
    fun main(args: Array) {
    println("Hello GOTO Chicago")
    }
    

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50. @TTGonda
    JS - INTELLIJ
    ▸ Create index.html that runs script
    <br/>
    <br/>
    ▸ Build > Build Application
    ▸ Open index.html in browser ▶
    

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51. @TTGonda
    JS - COMMAND LINE
    ▸ Library code is in library.kt
    kotlinc-js -output sample-library.js -meta-info library.kt
    ▸ Output:
    sample-library.js
    sample-library.meta.js
    

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52. @TTGonda
    JS - OTHER OPTIONS
    ▸ Gradle
    ▸ Maven
    

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53. @TTGonda
    VIEWS
    ▸ Use kotlinx.html library to interact with, and build HTML views
    ▸ Use Anko to build views for Android
    ▸ You can use Kotlin for the logic of what to display in your views!
    

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54. @TTGonda
    VIEWS
    ▸ kotlinx.html
    val myDiv = document.create.div {
    p { +"text inside" }
    }
    

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55. @TTGonda
    NATIVE
    ▸ Available for macOS, Linux and Windows
    ▸ LLVM
    ▸ Interop with C libraries
    

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56. @TTGonda
    NATIVE - COMMAND LINE
    ▸ Download compiler for your OS
    ▸ Create file hello.kt
    fun main(args: Array) {
    println("Hello GOTO Chicago")
    }
    ▸ Compile

    konanc hello.kt
    ▸ Run ▶

    /hello.kexe
    

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57. @TTGonda
    NATIVE - OTHER OPTIONS
    ▸ CLion IDE
    ▸ Gradle
    

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58. MULTI PLATFORM
    

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59. @TTGonda
    MULTI PLATFORM
    ▸ Share logic across platforms
    ▸ Write once, use everywhere
    ▸ Keep native for any framework components
    ▸ Note: experimental
    

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60. @TTGonda
    MULTI PLATFORM
    ▸ Common module with code shared across
    platforms
    ▸ Platform specific module
    ▸ “Interface” for the common code to call
    platform specific implementations
    http://developine.com/kotlin-native-ios-development-multiplatform-project/
    

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61. @TTGonda
    MULTI PLATFORM - INTELLIJ
    

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62. @TTGonda
    common

    Kotlin
    JVM

    Kotlin
    JS

    Kotlin
    *.class *.js
    

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63. @TTGonda
    // In common module
    expect class Dog(bar: String) {
    fun bark()
    }
    fun main(args: Array) {
    Dog(“Spot").bark()
    }
    // In platform module
    actual class Dog actual constructor(val name: String) {
    actual fun bark() {
    println(“$name says ruff”)
    }
    }
    

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64. @TTGonda
    GET STARTED!
    ▸ kotlinlang.org docs
    ▸ try.kotlinlang.org to try Kotlin in the browser
    ▸ kotlin.link to find anything Kotlin you might want
    ▸ github.com/vgonda/Talk-Resources my resources from this talk (and others)
    ▸ Kotlin Slack
    ▸ Find me online!
    

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65. THANKS!
    VICTORIA GONDA
    VICTORIAGONDA.COM
    

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