ActiveRecord::AssociationTypeMismatch

could you help me I how to identify where i am passing a string method
instead of the associated object.

could you help me I how to identify where i am passing a string method
instead of the associated object.

Look at the error you posted, it is telling you the file and line number

Colin

As I said before, you've probably got a form, with a field (probably a
select drop-down) that you've called "category", which should be
called "category_id".

Inspect your params data, and see if what is being passed to
update_attributes (I assume that's what's at line 45 of the
clistings_controller) is what you expect.