私はレールのこの部分にあまり詳しくないので、優しくしてください。
http://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#method-i-collection_select
the syntax is
collection_select(object, method, collection, value_method, text_method, options = {}, html_options = {})
If you were to change the second parameter (method
) to an actual method (rather than just the attribute that you want from the billing object) you can make the value whatever you would like.
If that doesn't work (or if you're not allowed to substitute the attribute for a method) then you may be able to make it work using the 5th or 6th parameters, value_method
and text_method
, which define what values should be applied to the tags.
Anyway, this answer is mostly to point you in (hopefully) the right direction, since I'm not certain of the method or how it works.
Good luck.