What is the most idiomatic way of expressing a class hierarchy in Kotlin? I found this blog post which used delegation, but I have heard that delegation is not a feature that many developers choose to use. Though in this case I can’t see the downside to it. My specific use case is a set of immutable classes where sub classes add additional properties only. Thanks!

The most idiomatic way to express a hierarchy of classes is by using plain inheritance.

True that you don’t need to use delegation to implement composition, but delegation does allow you to forgo chaining calls to properties:

A.prop

instead of

A.B.prop

. Well at least without having to write custom accessors.