Creating new child in nested routes - ruby-on-rails

Question

This one is driving me crazy. I've got a nested relationship between two models in my project, and I decided I did not want it to be shallow, since the child object (years) has no meaning outside the context of the parent (festivals).
So I sort of de-shallowed the relationship wherever I could find a reference to it, but I find myself unable to access the page to create a new child object.
Here's the url as I understand it should be: /festivals/1/years/new
from routes.rb:
resources :festivals do
resources :years
end
From years_controller.rb:
# GET festivals/1/years/new
# GET festivals/1/years/new.json
def new
#festival = Festival.find(params[:festival_id])
#year = #festival.years.build
respond_to do |format|
format.html # new.html.erb
format.json { render :json => #year }
end
end
And the button users press to get to the New page (on the Show page for the parent object):
<%= link_to 'Add Year', new_festival_year_path(#festival), :class => 'btn' %>
That takes the user to the correct URL, but I get:
No route matches {:action=>"show", :controller=>"years", :festival_id=>#<Festival id: 7, name: "Improganza", founded: nil, logo: "", mission: "This is that one that people spend a lot of money t...", city: "Honolulu", state_code: "HI", country_code: "US", created_at: "2013-07-26 14:49:19", updated_at: "2013-07-26 14:49:19">}
I created a new Rails project and set up scaffolds using Akria Matsuda's nested_scaffold gem, just to compare that output with my code... the resulting files look as I've shown here. I have no idea what I might be missing.
Just for good measure, the output of my rake routes:
festival_years GET /festivals/:festival_id/years(.:format) years#index
POST /festivals/:festival_id/years(.:format) years#create
new_festival_year GET /festivals/:festival_id/years/new(.:format) years#new
edit_festival_year GET /festivals/:festival_id/years/:id/edit(.:format) years#edit
festival_year GET /festivals/:festival_id/years/:id(.:format) years#show
PUT /festivals/:festival_id/years/:id(.:format) years#update
DELETE /festivals/:festival_id/years/:id(.:format) years#destroy
festivals GET /festivals(.:format) festivals#index
POST /festivals(.:format) festivals#create
new_festival GET /festivals/new(.:format) festivals#new
edit_festival GET /festivals/:id/edit(.:format) festivals#edit
festival GET /festivals/:id(.:format) festivals#show
PUT /festivals/:id(.:format) festivals#update
DELETE /festivals/:id(.:format) festivals#destroy
GET /festivals(.:format) festivals#index
POST /festivals(.:format) festivals#create
GET /festivals/new(.:format) festivals#new
GET /festivals/:id/edit(.:format) festivals#edit
GET /festivals/:id(.:format) festivals#show
PUT /festivals/:id(.:format) festivals#update
DELETE /festivals/:id(.:format) festivals#destroy

Answer 1

Try this:
<%= link_to 'Add Year', new_festival_year_path(#festival.id, :class => 'btn' %>
or
<%= link_to 'Add Year', new_festival_year_path({festival_id: #festival.id}, :class => 'btn' %>
according to the error you're getting
:festival_id=>#<Festival id: 7, name: "Improganza", founded: nil, logo: "", mission: "This is that one that people spend a lot of money t...", city: "Honolulu", state_code: "HI", country_code: "US", created_at: "2013-07-26 14:49:19", updated_at: "2013-07-26 14:49:19">}
the router is getting your whole festival param as the input for :festival_id

Answer 2

I think you are merging together the #new and #year actions in the years_controller and that might be causing some problems.
# GET festivals/1/years/new
# GET festivals/1/years/new.json
def new
#festival = Festival.find(params[:festival_id])
#year = #festival.years.build
end
def create
#festival = Festival.find(params[:festival_id])
#year = #festival.years.create(...)
#...fill in the rest of the method...
end
You also should update your link:
<%= link_to 'Add Year', new_festival_year_path(festival_id: #festival), :class => 'btn' %>
I created a short quiz on nested resources that might be helpful.

Answer 3

The answer was fairly silly. In my Rails server log (which I need to train myself to pay more attention to), I saw the some lines indicating a problem in line 63 of my _form.html.erb partial.
That line was:
<%= link_to t('.cancel', :default => t("helpers.links.cancel")),
festival_year_path(#festival), :class => 'btn' %>
Oops. Why I ever decided the "Cancel" button should take you to a year (that, of course, would not exist) is beyond me. I changed it to festival_path(#festival) and it's all good.
Thanks, everyone, for your help. I'm a newcomer to StackOverflow and to Rails in general. It really makes me feel welcome that I got such quick responses!