In Java, you’re probably used to writing code like this: String question = 'What's your name?'

To encourage people to sign up, during the registration process, the only information you ask for is an email address and a password.Let’s start with the basis of Kotlin, namely declaring variables. For instance, imagine that you’re writing code for the next great social network app. Possibly the most tempting time to use a null value is when a field in a class or method won’t be initialized immediately. Initialize var fields with Option, not null If you’re working with a Java library that returns null, convert it to an Option, or something else.When a method doesn’t produce the intended result, you may be tempted to return null.When a var field in a class or method doesn’t have an initial default value, initialize it with Option instead of null.There are several common situations where you may be tempted to use null values, so this recipe demonstrates how not to use null values in those situations: I just imagine that there is no such thing as a null, and write my code in other ways. Period.”Īlthough I’ve used null values in this book to make some examples easier, in my own practice, I no longer use them. Solutionĭavid Pollak, author of the book Beginning Scala, offers a wonderfully simple rule about null values: Tony Hoare, inventor of the null reference way back in 1965, refers to the creation of the null value as his “billion dollar mistake.” In keeping with modern best practices, you want to eliminate null values from your code. This is Recipe 20.5, “Scala best practice: Eliminate null values from your code.” Problem This is an excerpt from the 1st Edition of the Scala Cookbook (partially modified for the internet). show more info on classes/objects in repl.

Kotlin assign if not null