ordinal of sealed class subclass

ordinal.kt

sealed class Event {
  object One : Event()
  object Two : Event()
  data class Three(val int: Int) : Event()
}

inline fun <reified T : Any> T.ordinal() =
    T::class.java.superclass.classes.indexOfFirst { sub -> sub == this@ordinal::class.java }

fun testOrdinal() {

  val f = Event.One
  val s = Event.Two
  val t = Event.Three(123)

  val t2 = Event.Three(4444)

  println(f.ordinal())   //0
  println(s.ordinal())   //1
  println(t.ordinal())   //2
  println(t2.ordinal())  //2

}

This is a clever solution! One thing worth considering for others that come across this answer: depending on how you scope this, you'll now have an ordinal method available for every class which may not make a whole lot of sense outside of this specific context.