that possibility is missing for collection_select.
But for your described needs the select list should work perfectly, so
you don’t have to bother about shortcomings of collection_select lists
The best way to pre-select an item in a collection_select list is – as
far as I know – using a separate options_from_collection_for_select for
which you can define a selected_value as last parameter.
The downside, however, is that such a options list is working with
select_tag only. So you have to handle the return value a bit
differently in your controller (which should be no problem in most
cases).
Another drawback is the missing possibility of defining :include_blank
for neither select_tag nor options_from_collection_for_select (yet). But
you can add an empty item to top easily before passing the values hash
to the form helper.
A quick outline of this solution:
