You can't do that. You are building a case class that is not immutable and is a mix between services ("how I do/get/calculate things) and data (just data). 

So please split that in two part, one where you use services to get data in the form you want, and one other that is just a data structure, if possible immutable (I would really much more prefer immutable datastructure, but I think I remember that we didn't make  WB*Field that way...)