When doing a controller update operation, missing parameters are
treated as unchanged. This is a great convention but I'm not sure how
to handle this when using a collection_select.
If a user deselects all items in a the HTML select, nothing is sent on
the update action.
For example, if 2 items are selected I get
params[:selected_location_ids] == ["22", "242"]
if no items are selected the params[:selected_location_ids] is not
Is there a way to make the HTML form send an empty option when nothing
is selected so I can know if the user deselected everything vs an
alternate form not sending this information?