Stanfy MadCode #10From Java to Kotlin. From Objective-C to Swift.

by Oleksandr Tereshchuk and Alexander Voronov

Into New Language

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Development Environment

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[ ] IntelliJ IDEA 15 bundles the Kotlin

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[ ] Command line tools - http://try.kotlinlang.org/

import java.io.File

val folders = File(args[0]).listFiles { file -> file.isDirectory() } folders?.forEach { folder -> println(folder) }

$ kotlinc -script list_folders.kts <path_to_folder_to_inspect>

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[ ] Refactoring

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[ ] Playground & REPL

https://developer.apple.com/swift/blog/?id=24

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[ ] Backward Compatibility

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[ ] Bridging & Interoperability

● Nullability

● Lightweight Generics

● Kindof

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Project Design

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[ ] Configure Android projectJust follow simple guide: https://kotlinlang.org/docs/tutorials/kotlin-android.html

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[ ] Project Design

● Headers

● Modules

● Multiple Items per File

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Language Vector

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[ ] ConciseCreate a POJO with getters, setters, equals(), hashCode(), toString() and copy() in a single line:

data class Customer(val name: String, val email: String, val company: String)

Want a singleton? Create an object:

object ThisIsASingleton { val companyName: String = "JetBrains"}

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[ ] Safeval x: String? = "Hi"x.length // Does not compile.

val y: String = null // Does not compile.if (x != null) { x.length // Compiles! Not idiomatic just to get length!}

// Same as above (IntelliJ auto-suggested the change).x?.length

// Elvis operator.val len = x?.length ?: -1val len = x!!.length // Will throw if null. Rarely used.

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[ ] Versatile & Interoperable● 100% compatible with all JVM frameworks● 100% Java Interoperability● JavaScript compiler to target Node.js environment● Very small runtime and stdlib for Android development ~ 1MB

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[ ] Protocol-Oriented

https://developer.apple.com/videos/play/wwdc2015-408

“Swift Is a Protocol-OrientedProgramming Language”

– Dave Abrahams

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[ ] Values instead of References

VS

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[ ] Safety

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Language Features

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[ ] Lambdasval longest = max(strings, { a, b -> a.length() < b.length() })

val lengthFive = strings.filter { it.length == 5 }.sortBy { it }.map { it.toUpperCase() }

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[ ] Extension Methodsfun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = this[index1] // 'this' corresponds to the list this[index1] = this[index2] this[index2] = tmp}

val l = mutableListOf(1, 2, 3)l.swap(0, 2)

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[ ] Sealed classessealed class Expr { class Const(val number: Double) : Expr() class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr()}

fun eval(expr: Expr): Double = when(expr) { is Const -> expr.number is Sum -> eval(expr.e1) + eval(expr.e2) NotANumber -> Double.NaN // the `else` clause is not required because we've covered all the cases}

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[ ] Data classesdata class User(val name: String = "", val age: Int = 0)

/** fun copy(name: String = this.name, age: Int = this.age) = User(name, age)*/val adam = User("Adam", 35) val jane = adam.copy(name = "Jane") val (name, age) = janeprintln("$name, $age years of age") // prints "Jane, 35 years of age"

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[ ] Language Features

● First Class Functions

● Partial Application

● Generics

● Type Inference

● Enums

● Operators

● Standard Library

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Publishing

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[ ] Publishing

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[ ] AppStore Publishing

Built with xcodebuild Exported from Xcode Organizer

100384 21680

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Language Evolution

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[ ] Still in beta...● Sponsored and developed by JetBrains - https://kotlinlang.org/● Already have a huge community - Slack channel● Not as known as Scala or Groovy yet● Still in beta - syntax changes, missing features, hidden bugs● Using Project Kotlin for Android by Jake Wharton

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[ ] Stable

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[ ] OpenSource

github.com/apple

swift.org

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TODO

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[ ] KAPT pain● Annotation processing is not fully functional yet

○ Better Annotation Processing: Supporting Stubs in kapt● Mockito sometimes behaves wildly

○ How to use Mockito with Kotlin?● New testing framework - Spek

○ http://jetbrains.github.io/spek/● Extension functions break incremental compilation

○ All hopes for new beta

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[ ] Anko - https://github.com/Kotlin/anko

verticalLayout { val name = editText() button("Say Hello") { onClick { toast("Hello, ${name.text}!") } }}

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[ ] TODO

bottomLeftButton.performSelector( “_whyIsThisViewNotFocusable”)

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[ ] TODO

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Thanks!

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Happy Holidays!

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