Kotlin for Swift developers

Swift and Kotlin have a lot of concepts in common but they also have a few notable differences. Knowing both languages can help you write better code and share ideas between developers of “the other platform”. We will cover the basics of Kotlin before converting a Swift app into a Kotlin one. We will use concepts such as sealed classes, extensions and many others to make our code more robust and readable.

Accompanying blogpost: https://www.liip.ch/en/blog/app-builders-kotlin-swift-developers

Transcript

1. Hello
2. Who is a Swift developer ?
3. Who is a Kotlin developer ?
4. Welcome to Kotlin for Swift developers
5. Jonas Schmid • iOS / Android developer • I like both platforms and synergies between them
6. This talk is in two parts • Differences between Swift and Kotlin • Code demo: conversion from Swift to Kotlin
7. Buckle up We'll go fast
8. Let's go ! !
9. Variables and constants Swift var myVariable = 21 myVariable = 42 let myConstant = 21 Kotlin var myVariable = 21 myVariable = 42 val myConstant = 21
10. String interpolation in Swift let name = "Lugano" let message = "The name \(name) has \(name.count) letters" String templates in Kotlin val name = "Lugano" val message = "The name $name has ${name.length} letters"
11. Functions Swift func showAlert(title: String, _ description: String? = nil) {} showAlert(title: "Hello Lugano!", "Second best city in Switzerland") showAlert(title: "Hello Lugano!") Kotlin fun showAlert(title: String, description: String? = null) {} showAlert("Hello Lugano!", "Second best city in Switzerland") showAlert(title = "Hello Lugano!")
12. Classes: Swift class Person { var name: String? func greetings() -> String { return "Hello \(name ?? "stranger")" } } let person = Person() person.name = "Jonas" person.greetings()
13. Classes: Kotlin class Person { var name: String? = null fun greetings() = "Hello ${name ?: "stranger"}" } val person = Person() person.name = "Jonas" person.greetings()
14. Initializers: Swift class Car { var wheels: Int init(wheels: Int) { self.wheels = wheels } } let car = Car(wheels: 4) car.wheels
15. Constructors: Kotlin class Car( var wheels: Int ) { // ... } val car = Car(4) car.wheels
16. Structs: Swift struct Plane { var wings: Int } let plane = Plane(wings: 2)
17. Data classes: Kotlin data class Plane ( var wings: Int ) val plane = Plane(2)
18. Value type: Swift var plane1 = Plane(wings: 2) var plane2 = plane1 plane2.wings = 4 plane1.wings // 2
19. Reference type: Kotlin var plane1 = Plane(2) var plane2 = plane1 plane2.wings = 4 plane1.wings // 4
20. Extensions Swift extension Plane { func fly() { ... } } Kotlin fun Plane.fly() { ... }
21. Enums: Swift enum ApiResponse { case success(value: [Todo]) case failure(error: String) } Sealed classes: Kotlin sealed class ApiResponse data class Success(val value: List<Todo>) : ApiResponse() data class Failure(val error: String) : ApiResponse()
22. Pattern matching: Swift func handleResponse(_ response: ApiResponse<String>) { switch response { case .success(let value): print(value) case .failure(let error): os_log(error) } } let response = ApiResponse.success(value: "Hello") handleResponse(response)
23. Pattern matching: Kotlin fun handleResponse(response: ApiResponse<String>) { when(response) { is Success -> println(response.value) is Failure -> println(response.error) } } val response = ApiResponse.Success("Hello") handleResponse(response)
24. Type casting Let's set the base classes protocol Shape { func area() -> Double } struct Circle: Shape { var radius: Double func area() -> Double { return Double.pi * pow(radius, 2) } }
25. Type casting: Swift func displayShape(_ shape: Shape) { if let circle = shape as? Circle { print("Circle radius: \(circle.radius)") } print("Shape area: \(shape.area())") } let circle = Circle(radius: 3) displayShape(circle)
26. Smart casting: Kotlin fun displayShape(shape: Shape) { if (shape is Circle) { println("Circle radius: ${shape.radius}") } println("Shape area: ${shape.area()}") } val circle = Circle(3.0) displayShape(circle)
27. guard: Swift func playWithShape(shape: Shape) { guard let circle = shape as? Circle else { return } print("Circle radius: \(circle.radius)") }
28. return: Kotlin fun playWithShape(shape: Shape) { val circle = shape as? Circle ?: return println("Circle radius: ${circle.radius}") }
29. DEMO
30. Summary • Basics of Kotlin • Code conversion was fast • Swift and Kotlin are fairly similar • Lot of patterns from one can be used with the other • That was just a start
31. Everyone can grow by learning the other language
33. Jonas Schmid @jonas_schmid ✉ jonas.schmid@liip.ch See you at the App Builders party! Slides: liip.to/ab19