Kotlin Everywhere - Speaker Deck

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Kotlin Everywhere!

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Akshay Chordiya ● Founder of BitFurther ● Android Developer by heart ● Active community speaker ● Co-author of upcoming book “Kotlin Blueprints” ● Graduated in 2016 @Aky @Akshay_Chordiya AkshayChordiya

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Hardik Trivedi ● A Computer program writer ● Works at Globant ● Love writing tech blogs and contributing back to community ● Mentor college graduates and professional who wants to go for mobile app development ● Co-author of an upcoming book “Kotlin Blueprints” https://trivedihardik.wordpress.com/ hardik-trivedi

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Agenda ● What’s Kotlin? ● Why Kotlin? ● Syntax ● Future of Kotlin ● Platform walkthrough ● Conclusion ● Q&A

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What’s Kotlin?

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“Kotlin is a new programming language targeting JVM, Android and even JavaScript.”

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Kotlin ● Modern & Statically typed ● Targets JVM, Android, JavaScript and Native* ● Works everywhere where Java works ● 100% interoperable with Java™ ● Combines Object Oriented and Functional features ● Made by good folks at JetBrains ● Open source * denotes it’s still in preview

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Big Players using Kotlin Logos belong to respective company

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Kotlin Philosophy

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Kotlin Philosophy Concise Safe Interoperable Tooling Image credits - kotlinlang.org

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Kotlin Philosophy Concise Interoperable Tooling Image credits - kotlinlang.org Safe

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Kotlin Philosophy Concise Tooling Image credits - kotlinlang.org Safe Interoperable

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Kotlin Philosophy Concise Image credits - kotlinlang.org Safe Interoperable Tooling

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Kotlin Philosophy Concise Safe Interoperable Tooling Image credits - kotlinlang.org

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Why Kotlin?

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Why Kotlin ● It's a fun language! ● Tired of Java….JS ● Helps you be more productive ● Everywhere ● Push from Google and Android community ● Cool language features ● Functional nature

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Pillars of Functional Programming ● Explicitness ● Purity ● Immutability ● Concurrency ● Higher Order Functions

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Syntax Crash course

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Variables // String (Implicitly inferred) val spell = "Lumos" // Int val number = 74 // Explicit type var spells: List = ArrayList()

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“Use val for a value that won’t change” - Immutable val vs var “Use var for something that will vary with time.” - Mutable

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fun add(a: Int, b: Int): Int { return a + b } Functions fun add(a: Int, b: Int) = a + b fun add(a: Int = 0, b: Int = 0) = a + b

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Features

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Null Safety

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// Compile time error val spell: String = null // OK val spell: String? = null Declaring null variables

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// Compile time error var spell: String = "Lumos" spell = null // OK var spell: String? = "Lumos" spell = null Even...

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// Safe val spell: String? = null val length = spell?.length // Safe with else val length = spell?.length ?: -1 Kotlin-ized way

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Data Class

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User class - Java public class User { private String firstName; private String lastName; public User() { this.firstName = ""; this.lastName = ""; } // Getter - Setter, hashCode, equals(), and other stuff @Override public String toString() { return "User{" + "firstName='" + firstName + '\'' + ", lastName='" + lastName + '\'' + '}'; } } ~60 lines

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User class - Kotlin data class User(var firstName = "", var lastName = "") That’s it!

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Extension function

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fun String.isEmail(): Boolean { // this -> value of string return Patterns.EMAIL_ADDRESS.matcher(this).matches() } Extension Function

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Usage: Extension Function "[email protected]".isEmail() if("[email protected]".isEmail()) { // It's valid email address }

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Smart Cast

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Smart Cast // Java way if (text instanceof String) { int length = ((String) text).length(); } // Kotlin way if (text is String) { // Smart casting val length = text.length }

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String interpolation

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String interpolation fun sayHello(message: String) { println("Welcome $message") } fun sayTime() { println("Time: ${System.currentTimeMillis()}") }

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Future of Kotlin Image credits - Freepik

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The idea JVM Native iOS, etc. JS Kotlin Android *Native still in preview Spring, etc.

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The idea ● Android - Web - iOS teams will be able to work together, design together and solve problems together ● Enable Code sharing ● Easier development cycle with less hassle of maintaining multiple teams for each platform ● Easy to incorporate in your existing project. Thanks to the interoperability

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Kotlin For Android

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Kotlin for Android ● Jetbrains and Google, very much focused for Android. ● It’s becoming more and more popular. ● Philosophy and Spirit of Kotlin and Android are matching. ● Android is enabled with excellent tooling support from JetBrains and Google. ● Kotlin is perfect whose project still compiles on Java 6 and want to have fun with lucrative feature of Java 8 ● It has 100% interoperability with Java from day one. One can start using Kotlin in Java project on any moment of the day. ● It’s a mocktail with power of OOP language and beauty of functional programming language.

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Kotlin for Android ● Android is smart and language is smarter ● Kotlin has so much to offer for Android, it’s concise, expressive and powerful. ● With the Null Safety Kotlin actually eliminates the possibility of app crash. ● It’s concise, so it’s less line of code and less verbosity around the business logic. ● Co routines and delegates reduces great amount of code ● Anko is dedicated library from JetBrains which solves all Android problem ● Android loves ceremonies of API ● Lint also supports Kotlin.

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Kotlin for Android // Java Button myButton = findViewById(R.id.my_button); myButton.setText("Click"); // Kotlin import kotlinx.android.synthetic.main.activity_home.* myButton.text="Click"

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// Java Editor editor = sharedpreferences.edit(); editor.putString("key", "value"); editor.apply(); Kotlin for Android // Kotlin private var isConnectedToTwitter: Boolean by DelegatedPreference(this, IS_CONNECTED_TO_TWITTER, false)

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● No support for statics ● Extra runtime overhead ● Adds around 6K method count ● Increases the app size ● Mocking is the problem Kotlin for Android

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Kotlin For JS

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Kotlin for JavaScript ● Do not think support for JavaScript is on experimental basis. ● All Koltin features are fully supported ● Multiple ways to compile Koltin to Javascript ● Koltin’s package for JavaScript includes libraries which supports DOM element manipulation, and also Graphical elements using WebGL

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Kotlin for JavaScript ● Let’s understand how Koltin code gets converted in JavaScript import kotlin.browser.document fun main(args: Array) { document.bgColor="FF0000" val message = "Hello JavaScript!" println(message) }

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Kotlin for JavaScript ● Index.html will look like Console Output

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if (typeof kotlin === 'undefined') { throw new Error("Error loading module 'KotlinWeb'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'KotlinWeb'."); } var KotlinWeb = function (_, Kotlin) { 'use strict'; var println = Kotlin.kotlin.io.println_s8jyv4$; function main(args) { document.bgColor = 'FF0000'; var message = 'Hello JavaScript!'; println(message); } _.main_kand9s$ = main; Kotlin.defineModule('KotlinWeb', _); main([]); return _; }(typeof KotlinWeb === 'undefined' ? {} : KotlinWeb, kotlin);

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● Koltinx.html is a library which has DSL (Domain Specific Language) to write HTML ● You can build a DOM tree window.setInterval({ val myDiv = document.create.div("panel") { p { +"Here is " a("http://kotlinlang.org") { +"official Kotlin site" } } } document.getElementById("container")!!.appendChild(myDiv) document.getElementById("container")!!.append { div { +"added it" } } }, 1000L)

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● You can build HTML directly to System.out.appendHTML().html { body { div { a("http://kotlinlang.org") { target = ATarget.blank +"Main site" } } } }

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Kotlin Native

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Going native ● Kotlin without a VM! ● Compiles down to machine code ● Self-contained executable for iOS, macOS, Linux and Windows ● It uses LLVM compiler ● It’s still in preview! Not in a shippable state at all ● Interops with C ● It will be useful for building apps for iOS and embedded systems

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Conclusion

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“With Kotlin our code base is shrinked down.”

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“Plenty of app crashes are cut down”

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“Kotlin makes development more fun again”

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Further Resources ● All the images and logos used are trademarks of respective companies. ● Kotlin Official Website ● Kotlin and Android ● Getting started with Kotlin - Video ● Sample News App with 100% Kotlin ● Why Kotlin-ize your Android Development Medium - Akshay Chordiya ● Kotlin - Goodbye findViewById ● Easter Functions in Kotlin ● Being more productive with Kotlin

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Thank you! Slides: https://goo.gl/eTXGyL