package com.classLesson sealed class Person { // why compiler is complaining here class Men : Person() class Women : Person() abstract fun Sexuality() : String } class Men : Person() { override fun Sexuality(): String { return "M" } } class Women : Person() { override fun Sexuality(): String { return "F" } } // compiler should complain for this class Animal : Person() { override fun Sexuality(): String { return "shouldn't be allowed" } } fun main(args: Array<String>) { var a: Person = Animal() when (a) { is Men -> println("Men") is Animal -> println("Animal") } } @

Please surround your code with 3 backticks (`)

Compiler should complain about Animal because I am limiting my possible derived classes to be Men , Women only

Kotlin allows you to define subclasses either inside the sealed class or in the same file

Yeah so , I am defining my subclasses in the same file

And by the way, you are actually declaring the

Men

-class twice, first inside

Person

and a second time beneath it

So , you mean all the subclasses defined for a sealed abstract class inside the same file are valid . But they cannot be defined outside the file. Hence it does not Matter if I define my subclasses as "nested" inside the sealed class or as a top level class in the same file.

exactly

Thank you so much , understood sealed classes , seems really useful and powerful