Are Kotlin data classes Value types or Reference type?

Question

I am from Swift background. Swift has both "value" type & "reference" type support, I am bit curious. Does Kotlin have similar concepts?

By default, any class is a reference type. Whereas, with some digging, I found "data class" in Kotlin behaves as a value type.

I don't have clarity from official documentation. https://kotlinlang.org/docs/data-classes.html

Can some one please help in understanding this concept?

The difference between data classes and other classes is only a few automatically generated methods like toString, equals etc. In all other respects data class is just a regular class. — bylazy
– bylazy, Commented Apr 3, 2023 at 5:04

broot · Accepted Answer · 2023-04-03 08:06:30Z

4

Data classes in Kotlin don't differ that much from regular classes. They are represented and passed as a reference to an object on the heap.

Kotlin has a limited support for value/inline classes:

value class Password(private val s: String)

Unfortunately, as for now this is restricted to only a single field per class.

You can find more information in the KEEP, including reasoning on whether to support multiple fields before/after the Project Valhalla: https://github.com/Kotlin/KEEP/blob/master/notes/value-classes.md

answered Apr 3, 2023 at 8:06

broot

28.9k3 gold badges47 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1