How to use Manifest with Enumeration in Scala?

If I have the following Scala code:

trait BaseTrait[EnumType <: Enumeration] {
    protected val enum: EnumType
    protected val valueManifest: Manifest[EnumType#Value]
}

object MyEnum extends Enumeration {
    val Tag1, Tag2 = Value
}

And I want to create a class which implements BaseTrait using MyEnu开发者_运维百科m, I can do it like this:

class BaseClass[EnumType <: Enumeration]
(protected val enum: EnumType)
(implicit protected val valueManifest: Manifest[EnumType#Value])
extends BaseTrait[EnumType] {
}

class Test extends BaseClass(MyEnum)

But how can I do it without an intermediary base class? All other attempts always resulted in a compile error.

You did not write what you tried but my guess is that you had your class extend BaseTrait[MyEnum]. As MyEnum is an object the type MyEnum does not exist (unless you also define a class or trait with that name).

You have to explicitly supply the singleton type MyEnum.type as type parameter.

class Test extends BaseTrait[MyEnum.type] {
  protected val enum = MyEnum
  protected val valueManifest = manifest[MyEnum.type#Value]
}