Book Image

Functional Kotlin

Book Image

Functional Kotlin

Overview of this book

Functional programming makes your application faster, improves performance, and increases your productivity. Kotlin supports many of the popular and advanced functional features of functional languages. This book will cover the A-Z of functional programming in Kotlin. This book bridges the language gap for Kotlin developers by showing you how to create and consume functional constructs in Kotlin. We also bridge the domain gap by showing how functional constructs can be applied in business scenarios. We’ll take you through lambdas, pattern matching, immutability, and help you develop a deep understanding of the concepts and practices of functional programming. If you want learn to address problems using Recursion, Koltin has support for it as well. You’ll also learn how to use the funKtionale library to perform currying and lazy programming and more. Finally, you’ll learn functional design patterns and techniques that will make you a better programmer.By the end of the book, you will be more confident in your functional programming skills and will be able to apply them while programming in Kotlin.
Table of Contents (22 chapters)
Title Page
Copyright and Credits
Packt Upsell

Using coroutines in real life

Microbenchmarks are very funny and they give us an idea of the power of Kotlin coroutines, but they don't represent a real-case scenario.

Let's introduce our real-case scenario:

enum class Gender {

   companion object {
      fun valueOfIgnoreCase(name: String): Gender = valueOf(name.toUpperCase())

typealias UserId = Int

data class User(val id: UserId, val firstName: String, val lastName: String, val gender: Gender)

data class Fact(val id: Int, val value: String, val user: User? = null)

interface UserService {
   fun getFact(id: UserId): Fact

Our UserService interface has just one method—getFact will return a Chuck Norris-style fact about our user, identified by the user ID.

The implementation should check first on a local database for a user; if the user doesn't exist in the database, it should get it from the RandomUser API service, (, and then store for future use. Once the service has a user...