Switchable (table) sorting

I’m trying to implement a table with sorting its items. Currently I need to switch between sortedBy and sortedByDescending. How to make it optimal?

    fun sort(index: Int) {
        fun selector(it: Contract) = when (index) {
            0 -> it.country.name
            1 -> it.price
            else -> it.price

        items = if (index == sortIndex) items.sortedBy { selector(it) } 
          else items.sortedByDescending { selector(it) }
        sortIndex = index

UPD: Hm, looks like it’s the optimal solution. I just need to add a second variable. But I’m curious of multiple internal functions.