If you want a field to be able to be not-set, you just need to specify that by making it an `Option<_>` type. So like, if the field is a number, make it an `Option<u64>` -- that way you can distinguish between not-set (`None`) and set to zero (`Some(0)`).
Edit: whoops, misread which language it was you were frustrated with. Nevermind!
Edit: whoops, misread which language it was you were frustrated with. Nevermind!