RefId.kt

/**
* A type safe wrapper for comparable IDs 
**/


import java.util.UUID

abstract class RefId<T : Comparable<T>> : Comparable<RefId<T>> {
    abstract val value: T
    override fun compareTo(other: RefId<T>) = value.compareTo(other.value)
}

data class UsrId(override val value: UUID) : RefId<UUID>()
data class Usr(val id: UsrId)

fun main() {

    val uuid1 = UUID.randomUUID()
    val uuid2 = UUID.randomUUID()

    println(UsrId(uuid1) == UsrId(uuid1))
    println(UsrId(uuid1) == UsrId(uuid2))
}