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Hello
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Who is a Swift
developer ?
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Who is a Kotlin
developer ?
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Welcome to
Kotlin
for Swift developers
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Jonas Schmid
• iOS / Android developer
• I like both platforms and synergies between them
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This talk is in two parts
• Differences between Swift and Kotlin
• Code demo: conversion from Swift to Kotlin
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Buckle up
We'll go fast
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Let's go !
!
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Variables and constants
Swift
var myVariable = 21
myVariable = 42
let myConstant = 21
Kotlin
var myVariable = 21
myVariable = 42
val myConstant = 21
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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"
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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!")
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Classes: Swift
class Person {
var name: String?
func greetings() -> String {
return "Hello \(name ?? "stranger")"
}
}
let person = Person()
person.name = "Jonas"
person.greetings()
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Classes: Kotlin
class Person {
var name: String? = null
fun greetings() = "Hello ${name ?: "stranger"}"
}
val person = Person()
person.name = "Jonas"
person.greetings()
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Initializers: Swift
class Car {
var wheels: Int
init(wheels: Int) {
self.wheels = wheels
}
}
let car = Car(wheels: 4)
car.wheels
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Constructors: Kotlin
class Car(
var wheels: Int
)
{
// ...
}
val car = Car(4)
car.wheels
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Structs: Swift
struct Plane {
var wings: Int
}
let plane = Plane(wings: 2)
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Data classes: Kotlin
data class Plane (
var wings: Int
)
val plane = Plane(2)
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Value type: Swift
var plane1 = Plane(wings: 2)
var plane2 = plane1
plane2.wings = 4
plane1.wings // 2
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Reference type: Kotlin
var plane1 = Plane(2)
var plane2 = plane1
plane2.wings = 4
plane1.wings // 4
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Extensions
Swift
extension Plane {
func fly() { ... }
}
Kotlin
fun Plane.fly() { ... }
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Enums: Swift
enum ApiResponse {
case success(value: [Todo])
case failure(error: String)
}
Sealed classes: Kotlin
sealed class ApiResponse
data class Success(val value: List) : ApiResponse()
data class Failure(val error: String) : ApiResponse()
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Pattern matching: Swift
func handleResponse(_ response: ApiResponse) {
switch response {
case .success(let value): print(value)
case .failure(let error): os_log(error)
}
}
let response = ApiResponse.success(value: "Hello")
handleResponse(response)
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Pattern matching: Kotlin
fun handleResponse(response: ApiResponse) {
when(response) {
is Success -> println(response.value)
is Failure -> println(response.error)
}
}
val response = ApiResponse.Success("Hello")
handleResponse(response)
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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)
}
}
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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)
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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)
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guard: Swift
func playWithShape(shape: Shape) {
guard let circle = shape as? Circle else {
return
}
print("Circle radius: \(circle.radius)")
}
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return: Kotlin
fun playWithShape(shape: Shape) {
val circle = shape as? Circle ?: return
println("Circle radius: ${circle.radius}")
}
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DEMO
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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
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Everyone can grow
by learning
the other language
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No content
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Jonas Schmid
@jonas_schmid
✉
[email protected]
See you at the App Builders party!
Slides: liip.to/ab19