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

Extending Android framework using extension function


 The heading of this recipe might seem very confusing to you as you might be thinking "How can I extend the super complex Android framework? And moreover, why should I?" We will be dealing with all the "what, why, and hows" of extension functions in this recipe. Extension functions are one of the greatest features of Kotlin. So let's dive into it.

Getting ready

I'll be using Android Studio for coding. We will be creating extension functions for Android SDK classes.

How to do it…

To begin with, let's see a very simple example:

  1. We will create a very simple class Student, and we will create an extension function for it:
class Student(val age:Int)
  1. Now, we would want to create an isAgeGreaterThan20 function, which will return true if the age is greater than 20, or else, will return false. Now suppose there's a restriction that we can't touch the Student class, what will you do?
  2. In those scenarios, extension functions come in handy when you want to...