Book Image

Kotlin Programming Cookbook

By : Aanand Shekhar Roy, Rashi Karanpuria
Book Image

Kotlin Programming Cookbook

By: Aanand Shekhar Roy, Rashi Karanpuria

Overview of this book

The Android team has announced first-class support for Kotlin 1.1. This acts as an added boost to the language and more and more developers are now looking at Kotlin for their application development. This recipe-based book will be your guide to learning the Kotlin programming language. The recipes in this book build from simple language concepts to more complex applications of the language. After the fundamentals of the language, you will learn how to apply the object-oriented programming features of Kotlin 1.1. Programming with Lambdas will show you how to use the functional power of Kotlin. This book has recipes that will get you started with Android programming with Kotlin 1.1, providing quick solutions to common problems encountered during Android app development. You will also be taken through recipes that will teach you microservice and concurrent programming with Kotlin. Going forward, you will learn to test and secure your applications with Kotlin. Finally, this book supplies recipes that will help you migrate your Java code to Kotlin and will help ensure that it's interoperable with Java.
Table of Contents (21 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Using lazy delegate in Kotlin


The lazy construct is basically used for lazy initialization of properties, which is especially helpful when the object being initialized is a heavy object (takes time to initialize). Instantiating heavy objects at startup can cause visible performance drop in mobile user experience. Lazy initialization can solve our problem. In this recipe, we will learn how to use Kotlin's lazy delegate, so let's get started!

Getting ready

We will be using Android Studio 3.0 for coding, ensure that you have the latest version downloaded.

How to do it…

In the following steps, we will learn how to use the lazy delegate in Kotlin:

  1. First, let's see how to create a property through lazy initialization. The syntax is as follows:
val / var <property name>: <Type> by <delegate>
  1. While creating a lazy delegate, we use by lazy, as shown:
class MainActivity : AppCompatActivity() {
    private val textView : TextView by lazy {
        findViewById<TextView>(R.id.textView...