Book Image

Kotlin Quick Start Guide

By : Marko Devcic
Book Image

Kotlin Quick Start Guide

By: Marko Devcic

Overview of this book

Kotlin is a general purpose, object-oriented language that primarily targets the JVM and Android. Intended as a better alternative to Java, its main goals are high interoperability with Java and increased developer productivity. Kotlin is still a new language and this book will help you to learn the core Kotlin features and get you ready for developing applications with Kotlin. This book covers Kotlin features in detail and explains them with practical code examples.You will learn how to set up the environment and take your frst steps with Kotlin and its syntax. We will cover the basics of the language, including functions, variables, and basic data types. With the basics covered, the next chapters show how functions are first-class citizens in Kotlin and deal with the object-oriented side of Kotlin. You will move on to more advanced features of Kotlin. You will explore Kotlin's Standard Library and learn how to work with the Collections API. The book finishes by putting Kotlin in to practice, showing how to build a desktop app. By the end of this book, you will be confident enough to use Kotlin for your next project.
Table of Contents (15 chapters)
Title Page
Copyright and Credits
Packt Upsell

Building a simple DSL

We can now put to use what we learned about receiver and infix functions and create a DSL for validating objects. To keep it simple, we'll only be validatingInttypes.

First, we'll add the NumberValidator interface. This is where all the different validators can represent their validation logic:

interface NumberValidator 

fun isValueValid(value: Int): Boolean


Then, we need a type that will keep all the validators and the validated object. We'll name it Validator:

class Validator<T> private constructor(private val validatedObject: T) {

internal val validators = mutableListOf<NumberValidator>()
private lateinit var valueFactory: (T) -> Int

To enforce type safety, the Validator type is generic. It has a list of validators and also holds a function type called valueFactory, which knows how to return a property that will be validated. Notice how the constructor is private. We don’t allow the validator type to be created from outside; instead, we use an...