`sealed class` vs `enum` — when would you choose `sealed`?

Answer

Use `sealed` when you need a closed set of variants that can carry different data and types (sum type). It enables exhaustive `when` checks, while `enum` is a fixed set of instances of one type.

sealed interface Result

data class Ok(val value: Int) : Result

data class Err(val message: String) : Result

fun handle(r: Result) = when (r) {
  is Ok -> r.value
  is Err -> 0
}