Question

I’m trying to do something like this:

trait BaseMongoDAO[T <: IdentifiableModel with CaseClass] {


  implicit val manifest: Manifest[T]

  ........ some implicit manifest usage here
}


trait MongoUserRepository extends BaseMongoDAO[User] with UserRepository {

  override val manifest = Manifest.classType(User.getClass)

  ........ implementing UserRepository here

}

But it doesn’t seem to work and it says my Manifest is of incompatible type.

I did something wrong?

Answer 1

If we look at the definition of classType:

def classType[T](clazz: Predef.Class[_]): Manifest[T] =
    new ClassTypeManifest[T](None, clazz, Nil)

We can see that T is not inferred from the argument, and thus can only be inferred from the return type, or by explicitly giving the type parameter. The following should fix your issue:

override val manifest = Manifest.classType[User](User.getClass)

Alternatively:

override val manifest: Manifest[User] = Manifest.classType(User.getClass)