Demystify Kotlin

Google promoted Kotlin as a first class language on its Java-based Android platform back in May. Since then, the whole development world has been wondering: what is this language? Kotlin is the new lovechild of the JVM developers' world. In this session, we will going to discover the Kotlin language, starting from basics and making our way through the more difficult aspects of it.

Transcript

1. Chintan Rathod Demystify Kotlin
2. Mobile Team Lead Chintan Rathod Syx Automations India Pvt Ltd Event Organizer GDG Ahmedabad Follow +chintanrathod16 @chintanrathod16 Blog http://chintanrathod.com
3. What is Kotlin? Kotlin is statically typed programming language that targets the JVM, Android, JavaScript and Native. It's developed by JetBrains. The project started in 2010 and was open source.
5. Features • Null safety • Short & Sweet • Lamdas • Flexible • Mutability protection • Smart casts
6. Application Crashed !!
7. Null safety
8. Null safety • Explicitly requires to declare null var s : String = "Chintan" s = null // compilation error var s : String? = “Rathod" s = null // OK
9. Short & Sweet • Less number of code • Easy methods, functions and declarations view.setOnClickListener { view: View -> //do something }
10. Lamdas • Functional programming • Easy to write & express • Inlined • Neat clean code
11. Flexible • You can use Java class & libraries along with Kotlin as interoperability is very much between both languages.
12. Mutability protection • Mutability notation is required Either use VAR or VAL
13. var • Use var for something that will be changed • Mutable variables can be assigned multiple times
14. val • Use val for something won’t changed • Immutable variables can be assigned only single time (Constants)
15. var vs val var mutable : Int = 5 val immutable : Int = 5 mutable = 10 // Possible immutable = 10 // Not possible
16. Smart Casting Java Kotlin
17. How to start with Kotlin?
18. Android Studio 3.0+ It has in-built support of Kotlin For Android Studio 2.x version, you require to install plugin. You can do it by File -> Settings -> Plugin and search for “Kotlin”. Install it and restart your Android Studio.
20. Configure Gradle (Project)
21. Configure Gradle (Module)
22. That’s it!
23. Life with Kotlin 
24. Variables
25. Syntax Mutable variables var <object_name> : <Type> = <Value> Immutable variables val <object_name> : <Type> = <Value>
26. Declaration var i : Int = 1 var d : Double = 1.1 var f : Float = 1.1F var l : Long = 1L var c : Char = 'c' var s : String = "Chintan"
27. Any thing noticed?
28. Semicolons 
29. Strings var s = "Chintan" var ss = "My name is $s" // My name is Chintan var c = s[2] // this will assign character 'i'
30. Null safety var s : String = "Chintan" s = null // compilation error var s : String? = "Chintan" s = null // OK
31. Type cast val i : Int = 1 val d : Double = i // Not possible val d : Double = i.toDouble() // OK
32. Operators
33. Binary Expression Function a + b a.plus(b) a - b a.minus(b) a * b a.times(b) a / b a.div(b) a % b a.rem(b), a.mod(b) (deprecated) a..b a.rangeTo(b)
34. Operator Overriding data class Test(val count: Int) { operator fun plus(increment: Int): Test { return Test(count + increment) } } var test = Test(10) println(test + 10)
35. Operator Overriding data class Test(val count: Int) { operator fun plus(increment: Int): Test { return Test(count + increment) } } var test = Test(10) println(test + 10) // Output -> Test(count=20)
36. Unary Expression Function +a a.unaryPlus() -a a.unaryMinus() !a a.not()
37. Operator Overriding data class Test(val count: Int) operator fun Test.unaryMinus() = Test(-count) val test = Test(10) println(-test) // Output -> Test(count = -10)
38. Classes
39. Difference public class Student{ String name; Student(String name){ this.name = name; } public String getName(){ return name; } } class Student(val name: String) // That’s it. No more code
40. Properties class Student( // Read-only, generates field + getter val name : String, // Mutable, generates field + getter + setter var age : Int )
41. Properties var student = Student("Chintan Rathod", 28) println(student.name) // Output -> Chintan Rathod println(student.age) // Output -> 28
42. Constructor A class in Kotlin can have a primary constructor and one or more secondary constructors. The primary constructor is part of the class header: it goes after the class name (and optional type parameters). class Person constructor(firstName: String) { }
43. Constructor with code The primary constructor cannot contain any code. Initialization code can be placed in initializer blocks, which are prefixed with the init keyword: class Customer(name: String) { init { logger.info("Customer initialized with value ${name}") } }
44. Functions
45. No return // No return type. (can also be --> fun sayIt (a: String): Unit) fun sayIt (a: String) { println(a) }
46. Return value // With return type fun returnIt (returnable: String): String { return returnable }
47. Android Development
48. File extension • Java file has extension of .java • Kotllin file has extension of .kt
49. MainActivity.java public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); } }
50. MainActivity.kt class MainActivity : AppCompatActivity(){ override fun onCreate(savedInstanceState : Bundle?){ super.onCreate(savedInstanceState) } }
51. References • https://christinalee.github.io/Slides/slides-master/kotlin • https://speakerdeck.com/jakewharton/life-is-great-and-everything-will-be- ok-kotlin-is-here-google-io-2017 • https://try.kotlinlang.org • https://www.codementor.io/jussihallila/introduction-to-kotlin-part-1- 9mt0ony0g
52. Thank you! Slides posted: https://speakerdeck.com/chintanrathod