scala - How to access objects within an object by mixing in a trait with reflection?

Question

How can I get all of the objects within an object with reflection?

Consider this code:

object MonthDay extends MyEnum {
  //Some important holidays
  object NewYear       extends MonthDay( 1,  1)
  object UnityDay      extends MonthDay(11,  9)
  object SaintNicholas extends MonthDay(12,  6)
  object Christmas     extends MonthDay(12, 24)
}

class MonthDay(month: Int, day: Int)

trait MyEnum {
  val values: List[MonthDay] = this.getClass.getField("MODULE$")...
  val next: MonthDay = ...
  val previous: MonthDay = ...
}

//Of course the user can create his own MonthDays
val myBirthDay = new MonthDay(month, day)

if(!MonthDay.values.contains(myBirthDay)) "Well, I probably have to work"
else "Great, it is a holiday!"

I want to have a trait (MyEnum) which I can mix into the object holding my "enumeration objects" with methods to return a list of them (def values: List[MonthDay]) or iterate over them (def next: MonthDay or def previous: MonthDay) without repeating myself a few times (this is absolutely crucial!).

The idea is that values accesses the MonthDay object and finds all singleton objects of the class they are extending (MonthDay) with reflection.

Answer 1

Something similar is done in Enumeration.populateNameMap: https://lampsvn.epfl.ch/trac/scala/browser/scala/tags/R_2_8_1_final/src/library/scala/Enumeration.scala