In Scala, enums are a disputed area and many people (including myself) rather use case objects than any library-based enumeration. This is great, except for that one doesn't get a list of all possible values, which sometimes is needed. I've maintained such lists (allKeys) manually, but that is tedious and error-prone.
The question is: how can Scala 2.11 TypeTags or reflection be used, to create such a list?
One of two ways would work:
- getting all derived instances of a
sealedclass - getting all
case objects declared within a particular object
Note: There are samples that seem to promise what I'm looking for. But that's overkill - there must be an almost one-liner to get the same?
Below is a test for this. How could I implement the allOf function?
class ManifestToolsTest extends UnitTest {
behavior of "ManifestTools" {
sealed class MyEnum
object MyEnum {
case object A extends MyEnum
case object B extends MyEnum
case object C extends MyEnum
val x= 10 // should not be listed
def f(x: Int) = x // should not be listed
}
def allOf[T]: Seq[T] = {
...
}
it should "be able to list the 'case object' members of an object" in {
val tmp: Seq[MyEnum] = allOf[MyEnum]
tmp should contain theSameElementsAs( List(MyEnum.A, MyEnum.B, MyEnum.C) )
}
}
}
I've tried to get this info from the Scala documentation, but when it comes to reflection, things are really abstract. I believe the above need is (should be) covered by Scala 2.11.
References:
