how to handle null values in kotlin

Question

I have the following code

val book = Book(
                id!!,
                title!!,
                image!!,
                subtitle!!,
                author,
                "",
                0,
                0
            )

I don't want to use !!. What's the correct way to write this code given that each value might be null?

What do you want to happen if it is null? Do you have sane defaults to pass instead? If not, !! or a custom exception would be your best options. — Gabe Sechan, Mar 10 '20 at 03:42
https://stackoverflow.com/questions/37873995/how-to-create-empty-constructor-for-data-class-in-kotlin-android — IntelliJ Amiya, Mar 10 '20 at 03:46

score 1 · Accepted Answer · answered Mar 10 '20 at 05:01

If the values can be null, you should not prevent them from being passed in as null. We would say that those values are nullable and you can mark this by adding a question mark at the end of the type.

For example you could define the Book class as:

class Book(id: Int?, title: String?, ..)

and then you wouldn't need the force-unwrapping

val book = Book(id, title, image, subtitle, author, "", 0, 0)

But you might want to clarify what the last three values there are :)

how to handle null values in kotlin

1 Answers1