Hi. I'm a newbie Rails developer who is getting the following error when trying to access the 'new' action on my CityController:

undefined method `cities_path' for #<#<Class:0x104608c18>:0x104606f08>
Extracted source (around line #2): 
1: <h1>New City</h1>
2: <%= form_for(@city) do |f| %>
3:   <%= f.error_messages %>
4: 
5:   <div class="field">

As some background, I have a State model with many Cities. I'm getting this error after clicking on the following link coming from a State show page:

<p>Add a city: <%= link_to "Add city", new_state_city_path(@state) %></p>

When I run 'rake:routes' it says this is a legit route...

For more background, here is the CityController 'new' action:

def new
@city = City.new

respond_to do |format|
  format.html # new.html.erb
  format.xml  { render :xml => @city }
end
end

Here is the (complete) form in the view:

<%= form_for(@city) do |f| %>
<%= f.error_messages %>

<div class="field">
  <%= f.label :name %><br />
  <%= f.text_field :name %>
</div>
<div class="actions">
  <%= f.submit %>
</div>
<% end %>

This initially made me think that it's a resources/routes issue since it came back with a mention of 'cities_path' (in fact, that's what another person posting to Stack Overflow had wrong (http://stackoverflow.com/questions/845315/rails-error-nomethoderror-my-first-ruby-app). However, that doesn't seem to be the case from what I can see. Here are how my resources look in my routes file:

resources :states do
  resources :cities
end

I can get it working when they are not sub-resources, but I really need to keep them as sub-resources for my future plans with the app. Any help would be very much appreciated, since I've been racking my brains on this for more hours than I would care to admit... Thanks!

(Not sure this matters at all, but I'm running the very latest version of Rails 3 beta2).