Validate username uniqueness (to-do: extend with test for predefined path list)

unique_user.scala

class User extends MongoRecord[User] with MongoId[User] { 
  def meta = User 

  protected def valUnique(msg: String)(value: String): 
List[FieldError] = { 
    Console.println("Not the overloaded.") 
    Nil 
  } 

  object userName extends StringField(this, "") { 
    override def validations = 
      meta.valUnique("Username already taken.") _ :: 
        valMinLen(6, "Username cannot be shorter than 6 characters.") _ :: super.validations 
  } 
} 

object User extends User with MongoMetaRecord[User] { 
  override def valUnique(msg: String)(value: String): List[FieldError] = { 
    Console.println("Overloaded.") 
    if (this.find("userName", value).isDefined) 
      List(FieldError(this.userName, msg)) 
    else 
      Nil 
  } 
}