interface INamed {
    val name: String
}

class Flower(override val name: String): INamed

class City(override val name: String): INamed

class Star(override val name: String): INamed

val rows = arrayOf<INamed>(
    Flower("Rose"),
    City("Rome"),
    Star("Sirius")
)

val list = rows.joinToString { it.name }
//list is "Rose, Rome, Sirius"

println("list is '$list'")