Scala Language Enumerations
Remarks
Approach with sealed trait and case objects is preferred because Scala enumeration has a few problems:
- Enumerations have the same type after erasure.
- Compiler doesn't complain about “Match is not exhaustive", if case is missed it will fail in runtime
scala.MatchError:
def isWeekendWithBug(day: WeekDays.Value): Boolean = day match {
case WeekDays.Sun | WeekDays.Sat => true
}
isWeekendWithBug(WeekDays.Fri)
scala.MatchError: Fri (of class scala.Enumeration$Val)
Compare with:
def isWeekendWithBug(day: WeekDay): Boolean = day match {
case WeekDay.Sun | WeekDay.Sat => true
}
Warning: match may not be exhaustive.
It would fail on the following inputs: Fri, Mon, Thu, Tue, Wed
def isWeekendWithBug(day: WeekDay): Boolean = day match {
^
More detailed explanation is presented in this article about Scala Enumeration.
