Refactoring to Kotlin

A presentation on Kotlin features and how you can convert your existing Java codebase to Kotlin using them.

Transcript

1. Refactoring to Kotlin
2. Who am I? Jubril Edu Software Engineer @ Cotta & Cush Android & iOS @TheJubril Love running and exploring new places
3. • Kotlin features • Refactoring to Kotlin
4. About Kotlin • Unveiled in 2011 • Version 1.0 released in 2016 • Open Source • Interoperable with Java • Compiles to JVM bytecode and Javascript • Statically typed
5. Kotlin features Constructors: // Primary Constructor class Person constructor(firstName: String) { ... } // Secondary Constructor class Person { constructor(firstName: String) { ... } }
6. Kotlin features Collection Types: //immutable interface val articles = setOf("a", "A", "an", "An", "the", "The") val numbers = listOf("one", "two", "three", "four") val numbersMap = mapOf("key1" to 1, "key2" to 2, "key3" to 3, "key4" to 1) //mutable interface val set = mutableSetOf(1, 2, 3) val numbers = mutableListOf(1, 2, 3, 4) val numbersMap = mutableMapOf("one" to 1, "two" to 2)
7. Kotlin features Null Safety: var a: String = "abc" a = null // compilation error var b: String? = "abc" b = null // ok print(b) val l = b?.length ?: -1 // Using Elvis Operator val l = b?.length // Using Safe Call val l = b!!.length // Non null Operator
8. Kotlin features Data Classes: data class User(val name: String, val age: Int) Data classes have to fulfill the following requirements: • The primary constructor needs to have at least one parameter; • All primary constructor parameters need to be marked as val or var; • Data classes cannot be abstract, open, sealed or inner;
9. Kotlin features String Templates: val i = 10 println("i = $i") // prints "i = 10" val s = "abc" println("$s.length is ${s.length}") // prints "abc.length is 3" Type Check and Casts: if (obj is String) { print(obj.length) } fun demo(x: Any) { if (x is String) { print(x.length)//x is automatically cast to String } }
10. Kotlin features Singletons: object DataProviderManager { fun registerDataProvider(provider: DataProvider) { // ... } } Companion Objects: class MyClass { companion object Factory { fun create(): MyClass = MyClass()} } val instance = MyClass.create()
11. Kotlin features • Higher Order Functions • Lambdas • Coroutines
12. Refactoring from Java to Kotlin MVP • Interfaces • Activity • Data class • Presenter • Helper Class
13. Interfaces
14. Data Class
15. Adapter
16. Database Helper
17. Presenter: Kotlin 67 LOC Java 84 LOC Activity: Kotlin 97 LOC Java 118 LOC
18. Links Kotlin: https://github.com/djubreel/SimpleTodoAppKotlin Java: https://github.com/djubreel/SimpleTodoListJava
20. Questions