Ecto join and order_by with dynamic values

Hey fellow Elixirians!

I am having trouble with joining and ordering, but with dynamic values. So basically I send a dynamic “asc” or “desc” and a dynamic field to the function and it needs to order according to whats given. The problem is, that you can’t really put dynamic values in the ecto queries.. Or maybe I am doing it wrong. But in any case, here is my code:

def with_ordering(query, filters, orderable_fields) do
if Map.has_key?(filters, "order") and filters["order"] in @order_types do
  order_by =
    if Map.has_key?(filters, "order_by") and filters["order_by"] in orderable_fields do
      String.to_atom(filters["order_by"])
    else
      :inserted_at
    end

  from(
    ue in query,
    join: e in assoc(ue, :event)
    order_by: ["#{filters["order"]}": ^order_by]
  )
else
  query
end

end

Next to not being able to do certain things in the query, how can I order_by “e” with the dynamic value?

I am trying to achieve the following results dynamically:

from(
    ue in query,
    join: e in assoc(ue, :event)
    order_by: [asc: e.id]
  )

Any tips, best practices, tricks and hacks are appreciated!