Kotlin Enum with Custom Property and Converter

EnumConverter.kt

abstract class EnumConverter<in V, E: Enum<E>>(
        private val valueMap: Map<V, E>
) {
    fun fromValue(value: V): E? = valueMap[value]
    fun fromValue(value: V?, default: E): E = valueMap[value] ?: default
}

inline fun <V, reified E: Enum<E>> buildValueMap(keySelector: (E) -> V): Map<V, E> =
        enumValues<E>().associateBy(keySelector)

inline fun <V, reified E> buildValueMap(): Map<V, E> where E: Enum<E>, E: HasValue<V> =
        enumValues<E>().associateBy { it.value }

interface HasValue<out T> {
    val value: T
}

Size.kt

enum class Size(override val value: Int): HasValue<Int> {
    SMALL(0), MEDIUM(1), LARGE(2);
    companion object : EnumConverter<Int, Size>(buildValueMap())
}

// println(Size.fromValue(0))              // SMALL
// println(Size.fromValue(10, Size.LARGE)) // LARGE