The problem is it isn't declared, but somewhere something is trying to
The scaffold can be nice as a quickstart, but as you're trying to do
something new you're going to have to make changes to the views (and
the controllers too if they use named routes instead of :action
=> :whatever redirects).
A few things to try while tracking it down:
Look at the dev log (or your script/server output) for more
information on the error. It should mention view templates in there
somewhere, and that'll help you find the file & line number to blame.
The stack trace should be in the browser error page as well if you are
in development mode.
Project search for the text contact_path and change it to
admin_contact_path or whatever is appropriate
Look for any forms that are using @contact instead of [:admin,
(the symbol tells it about the routing namespace).