A case of Kotl.in

A presentation about basics of Kotlin, inspired by sessions from Jake Wharton and Rusell Winders

Transcript

2. A case of Kotl.in Rachit Mishra @rachitkmishra
3. Intro Statically typed language by Jetbrains since 2011 V1 around 2016 Interoperable Concise
4. Intro Statically typed language by Jetbrains since 2011 V1 around 2016 Interoperable Concise Statically typed language by Jetbrains since 2011
5. Intro Statically typed language by Jetbrains since 2011 V1 around 2016 Interoperable Concise V1 around 2016
6. Intro Statically typed language by Jetbrains since 2011 V1 around 2016 V1 around 2016 Interoperable Concise Interoperable
7. Why Kotlin Java is slow in evolution Java is not to so great on Android A lot of Util classes Null Pointer Exceptions
8. Why Kotlin Java is slow in evolution Java is not to so great on Android A lot of Util classes Null Pointer Exceptions
9. Why Kotlin Java is slow in evolution Java is not to so great on Android A lot of Util classes Null Pointer Exceptions
10. Why Kotlin Java is slow in evolution Java is not to so great on Android Lots of Util classes Null Pointer Exceptions
11. Hello world fun main(args: Array<String>) { val myName = "World" println("Hello $myName"} println("I am ${myName.length + 8} years old"} }
12. Hello world fun main(args: Array<String>) { val myName = "World" println("Hello $myName"} println("I am ${myName.length + 8} years old"} } fun main(args: Array<String>) { val myName = "World" println("Hello $myName"} println("I am ${myName.length + 8} years old"} } $myName ${myName.length + 8}
13. Immutability, Type Inference var myVar : String = "SomeAwesomeValue" val myVal : String = "SomeImmutableValue"
14. Immutability, Type Inference var myVar : String = "SomeAwesomeValue" val myVal : String = "SomeAwesomeValue" var myVar : String = "SomeAwesomeValue"
15. Immutability var myVar = 123 var myVar : String = "SomeAwesomeValue" val myVal = "Raju" Immutability, Type Inference Immutability, var myVar : String = "SomeAwesomeValue"
16. Expressions String x = null if (myAwesomeValue != null) { x = “myAwesomeValue” } else { x = “somethingElse” } var x = if (myAwesomeValue != null) { "myAwesomeValue" } else { "somethingElse" }
17. String x = null if (myAwesomeValue != null) { x = “myAwesomeValue” } else { x = “somethingElse” } String x = null if (myAwesomeValue != null) { x = “myAwesomeValue” } else { x = “somethingElse” } Expressions var x = if (myAwesomeValue != null) { "myAwesomeValue" } else { "somethingElse" }
18. String myString = null switch(someCase) { case 1: myString = "NewString"; break; case 2: myString = "SomeOtherString"; } Expressions var x = when (myVar) { !is X -> doSomething() “AwesomeValue” -> { reallyDoSomething() } else -> “FTW” } String myString = null switch(someCase) { case 1: myString = "NewString"; break; case 2: myString = "SomeOtherString"; }
19. String myString = null switch(someCase) { case 1: myString = "NewString"; break; case 2: myString = "SomeOtherString"; } Expressions var x = when (myVar) { !is X -> doSomething() “AwesomeValue” -> { reallyDoSomething() } else -> “FTW” } String myString = null switch(someCase) { case 1: myString = "NewString"; break; case 2: myString = "SomeOtherString"; } var x = when (myVar) { !is X -> doSomething() “AwesomeValue” -> { reallyDoSomething() } else -> “FTW” } String myString = null switch(someCase) { case 1: myString = "NewString"; break; case 2: myString = "SomeOtherString"; }
20. Fun: extension, high order, lambda fun String.toSnackCase() : String { return this.split(" ").joinToString("_") } "The King".toSnackCase() // outputs The_King fun Activity.isAlive() = !this..isFinishing()
21. Fun: extension, high order, lambda //a high order function with lambda/function receiver fun unaryOp(num1: Int = 2, op: (Int) -> Int) { println(op(num1)) } unaryOp(2) { it*it ) unaryOp(2, {x -> x*2})
22. Fun: extension, high order, lambda //a high order function with lambda/function receiver fun unaryOp(num1: Int = 2, op: (Int) -> Int) { println(op(num1)) } Int = 2 unaryOp(2) { it*it ) unaryOp(2, {x -> x*2}) //a high order function with lambda/function receiver fun unaryOp(num1: Int = 2, op: (Int) -> Int) { println(op(num1)) }
23. Fun: extension, high order, lambda //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } op: (Int) -> Int unaryOp(2) { it*it ) unaryOp(2, {x -> x*2})
24. Fun: extension, high order, lambda //a high order function with lambda fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } unaryOp(2, {x -> x*2}) unaryOp(2) { it*it ) unaryOp(2, {x -> x*2})
25. Fun: extension, high order, lambda //a high order function with lambda fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } unaryOp(2, {x -> x*2}) unaryOp(2) { it*it ) unaryOp(2, {x -> x*2}) unaryOp(2, {x -> x*2}) {x -> x*2} unaryOp(2, {x -> x*2}) fun sum(num: Int) { return num*num } unaryOp(2, ::sum)
26. Fun: extension, high order, lambda //a high order function with lambda fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } unaryOp(2, {x -> x*2}) unaryOp(2) { it*it } unaryOp(2, {x -> x*2}) unaryOp(2, {x -> x*2}) {x -> x*2} unaryOp(2, {x -> x*2}) fun sum(num: Int) { return num*num } unaryOp(2, ::sum)
27. Fun: extension, high order, lambda //a high order function with lambda fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } unaryOp(2, {x -> x*2}) unaryOp(2) { it*it ) unaryOp(2, {x -> x*2}) unaryOp(2, {x -> x*2}) {x -> x*2} unaryOp(2, {x -> x*2}) fun sum(num: Int) { return num*num } unaryOp(2, ::sum)
28. Fun: extension, high order, lambda //a high order function with lambda fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } unaryOp(2, {x -> x*2}) unaryOp(2) { it*it ) unaryOp(2, {x -> x*2}) unaryOp(2, {x -> x*2}) {x -> x*2} unaryOp(2, {x -> x*2}) fun sum(num: Int) { return num*num } unaryOp(2, ::sum)
29. Fun: extension, high order, lambda //a high order function with lambda fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } //a high order function with lambda/function receiver fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } unaryOp(2, {x -> x*2}) unaryOp(2) { it*it ) unaryOp(2, {x -> x*2}) unaryOp(2, {x -> x*2}) {x -> x*2} unaryOp(2, {x -> x*2}) fun sum(num: Int) { return num*num } unaryOp(2, ::sum) ::sum unaryOp(2, ::sum)
30. Nullability & Type Safety if(someObject != null) { if(someObject.someChild != null) { println(someChild.someValue) } }
31. Nullability & Type Safety if(someObject != null) { if(someObject.someChild != null) { println(someChild.someValue) } } var myObject : String? mObject.someValue // this won't compile mObject?.someValue // this will compile mObject?.myChildObject?.someValue // this will compile mObject!!.someValue // this will compile if(someObject != null) { if(someObject.someChild != null) { println(someChild.someValue) } }
32. Nullability & Type Safety myVar = myNewVar as? String var myVar: String = "Hello" val myNewVar: Int = 1 myVar = myNewVar as String // what will happen?
33. Nullability & Type Safety myVar = myNewVar as? String val myVar: String = "Hello" val myNewVar: Int = 1 myVar = myNewVar as String // what will happen? val myVar: String = "Hello" val myNewVar: Int = 1 myVar = myNewVar as String // what will happen?
34. Class, object, interface, data class class Person class Person() { } class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } } open class Person() { } val Person = Person()
35. Class, object, interface, data class class Person class Person() { } class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } } open class Person() { } val Person = Person() class Person class Person() { } class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } } open class Person() { } val Person = Person() class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } }
36. Class, object, interface, data class class Person class Person() { } class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } } open class Person() { } class Person class Person() { } class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } } open class Person() { } val Person = Person()
37. Class, object, interface, data class class Person class Person() { } class Person(val name : String = "SomeDefaultValue") { init { name = name.toSnackCase() } } open class Person() { } val Person = Person()
38. Class, object, interface, data class // object class object MyObject { var myVar: String = "Some constant" fun myObjectFunction() { } } // interface with method interface MyInterface { fun myInterfaceFunction() { } }
39. Class, objec, interface, data class // object class object MyObject { var myVar: String = "Some constant" fun myObjectFunction() { } } // interface with method interface MyInterface { fun myInterfaceFunction() { } } // object class object MyObject { var myVar: String = "Some constant" fun myObjectFunction() { } }
40. Class, interface, object class, data class // data class data class Person(var name: String = “Nishant Shah”, var age: Int) class Person { private String mName; private int mAge; getName() getAge() setName() setAge() equals() hashCode() } class Person { private String mName; private int mAge; getName() getAge() setName() setAge() equals() hashCode() }
41. Class, interface, object class, data class // data class data class Person(var name: String = “Nishant Shah”, var age: Int) class Person { private String mName; private int mAge; getName() getAge() setName() setAge() equals() hashCode() } class Person { private String mName; private int mAge; getName() getAge() setName() setAge() equals() hashCode() }
42. Kotlin Std Library PreConditions.checkNotNull(someValue) with(someCondition) { // do something } val myVal:String? = "Rachit" myVal?.let{ println(it) }
44. Caveats Lambda function inline keyword inline fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) }
45. Caveats Lambda function inline keyword inline fun unaryOp(num1: Int, op: (Int) -> Int) { println(op(num1)) } inline keyword
46. Caveats Nullabillity fun add(a: Int?, b: Int?): Int { return (a ?: 0) + (b ?: 0) } Burden of boxing and unboxing variables
47. Thank you ...
48. Resources kotlin.link https://developer.android.com/kotlin/resources.html https://medium.com/@BladeCoder/exploring-kotlins-hidden-costs-part-1-fbb9935d9b62 Practo Pro https://play.google.com/store/apps/details?id=com.practo.droid