val scoreSeq_opition: Seq[Option[String]] = List(Some("ngksf"),Some("fmgfdmg"),Some("mbmd"),None)
val nullOrdering: Ordering[Option[String]] = ????

I would like to sort by Ordering[Option[String]] if the above code. In that case, unlike the standard, we want None to be listed after Some, and Option[String] should be in the normal sort order for String. Last time we sorted strings in Score, but this time we are simply sorting strings of strings.

CodePudding user response：

For Option[String] it looks like this:

implicit val ord: Ordering[Option[String]] =
   Ordering.by(x => (x.isEmpty, x.getOrElse("")))

I am presuming that Score is just a type alias for Option[String] otherwise you need to create an Ordering[Score] with the appropriate rules. In that case the ordering can be in the companion object where the compiler will find it if it needs it.