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Kotlin presentation
This document provides an introduction and overview of the Kotlin programming language from the perspective of an Android engineering manager. It discusses that Kotlin is a programming language that runs on the JVM and was created by JetBrains as an alternative to Java for Android development. The document then covers various Kotlin concepts and features such as syntax, OOP concepts, properties, loops, lambdas, extensions and more in a conversational FAQ format. It also provides some useful Kotlin resources for learning more.
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Kotlin presentation
- 2. Who am I? Corneliu Balaban Mobile Engineering Manager @ Avira Romania Android aficionado with BI background Catching up on the “Kotlin for iOS” – Swift Passionate about BioMedical and AgriTech
- 3. What is this… Kotlin? It is a Russian Island close to St. Petersburg Initially belong to Sweden but after Russia annexed it and … Inspired the name for a new programming language running in the JVM Created by JetBrains, creators of PhpStorm, WebStorm, PyCharm etc Ads small overhead to the Android dev env and dex method count increase by ~6k methods
- 4. What have we beenmissing inJava? No need for functional interfaces in order to implement own higher functions and lambda’s Embedded lists iterators and mapping functions Class extensions (well… Swift has them) Strongly typed with inferred data types No elegant ways of avoiding NPE’s
- 5. Basic Kotlin syntax fun sayHello(name:String): Unit { print("Hello ${name}!" + "Welcome to Bucharest Mobile Meetup"); } OR fun sayHello(name: String): Unit = print("Hello ${name}!" + "Welcome to Bucharest Mobile Meetup"); OR fun sayHello(name: String) = print("Hello ${name}!" + "Welcome to Bucharest Mobile Meetup");
- 6. OOP concepts Kotlin classes Inherit from Java’s equivalent of Object Any By default are final Inheritance is enabled by prefixing the class with "open" Primary constructor is embedded in the class signature . It cannot contain any code Secondary constructors are available. Need to delegate to primary constructor init() methods come to the rescue Immutable variables are represented by the prefix "val" and can have inferred data type
- 7. OOP concepts Good ol'"bean" Easily accessible via "data classes" Makes a good separation of code if you want some objects that just need to hold data Can make use of companion objects to hold “static” values
- 8. MoreOOP … Javadevelopers love to be "static" Bad luck, there are no class level methods "Companion objects" are the new black Used to replicate "statics" behavior in Kotlin Can be one per class Static variables are not available other than via " companion objects
- 9. var, val …do I need to know them? Immutable objects/ variables are prefixed with "val" Can be initialized at declaration time. No data type needed as inference works as a charm If they cannot be initialized at declaration time then data type is mandatory Are there other kinds of immutable objects? var toDoList1: List<ToDoModel> = listOf(ToDoModel(name="Buy Milk"),ToDoModel(name="Buy Weed")); • var toDoList: MutableList<ToDoModel> = mutableListOf()
- 10. If val reffersto immutable, do I have project level constants Compile time constants are defined using the prefix "const” Cannot have a custom getter Can be used in annotations Can only be of type String or another primitive Can or cannot be part of a class/ object Immutable and mutable properties have intrinsic get and set methods You can customize the visibility of the setter and or getter as well as their behavior Since properties need to be assigned values at compile time, the only way to define properties that can receive runtime values is by using the prefix "lateinit"
- 11. Optionals & null safe accessors Swift has them so why not Kotlin as well They are some weird implementation of Schroedingers cat Optional properties can contain a value or can be null Methods can return optionals as well • To access potentially null variables/ objects you can use ?. • In chaining if at least one of the conditions is null then the entire chained expression is null
- 12. Loops, operator overloading and string interpolation Iteratingcollections is easier with " for – in " loops . No more of the Java " for – each" nightmare Range loops are introduces to help us run code for exact number of times " for i in 1 .. 27" Operator overloading has been made available yet by another language running on top on the JVM ( as did Groovy) String templates and interpolations are yet another valuable
- 13. Lambdas and higher order functions Introduced in Java 8 but cumbersome to use.Why? Cumbersome to introduce as functional interfaces are needed Not backwards compatible Not really useful for Android developers as we are still stuck on Java 7 Lambdas are natively supported by Kotlin Kotlin allows methods that can receive other functions as parameters Also it allows the existence of functions outside classes which is perfect for utils
- 14. Extensions Imagine that"String" would have an … ”getGreetingById" method Extensions can be used to add custom methods to existing objects They can be called as : Object. getGreetingById(1) Very similar to Swift extensions
- 15. Useful resources Must trythe "anko" library: https://github.com/Kotlin/anko Get dirty with Kotlin Koans here: http://try.kotlinlang.org/#/Kotlin%20Koans/Introduction/Strings/T ask.kt Try reading Antonio Leiva's Kotlin book: https://leanpub.com/kotlin-for-android-developers
- 16. Oh, and one morething … adding Kotlin to your project Not going through all the steps ;) Check them here: https://blog.jetbrains.com/kotlin/2013/08/working-with-kotlin-in- android-studio/
- 17.