Routing Error No route matches {:action=>"show" - ruby-on-rails

Question

I only have 2 weeks learning ruby on rails, in my app the users can register their cars, from their profile (code below) the app sent to the registration cars page,
<div class="container">
<fieldset>
<h1><%= #user.email %></h1>
<br>
<h2>now you are able to...</h2>
<br>
<ul>
<li>
<strong>new car registration: </strong>
<%= link_to "new car", new_user_car_path(current_user)%>
</li>
</ul>
</fieldset>
</div>
it works before but i don't know what i did that now it show this:
Routing Error
No route matches {:action=>"show", :user_id=>#<User id: 27, email: "armando.santoya#hotmail.com", encrypted_password: "$2a$10$EZtvPWiXgMfUlAqvuvGAzODMaas/y4rGkJPKJtg4PnC6...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 1, current_sign_in_at: "2012-07-24 19:07:54", last_sign_in_at: "2012-07-24 19:07:54", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", name: nil, created_at: "2012-07-24 19:07:54", updated_at: "2012-07-24 19:07:54">, :controller=>"cars"}
Try running rake routes for more information on available routes.
also I put my carsController
class CarsController < ApplicationController
def new
#car = Car.new
end
def create
#car = current_user.Car.new(params[:car])
if #car.save
flash[:notice] = "new car created success"
#redirect_to current_user, :flash => { :success => "car created!" }
else
#redirect_to new_user_car_path,
flash[:notice] = "sorry try again"
end
end
def index
#car=Car.all
end
def show
#car = current_user.car.find(params[:id])
##car = Car.find(params[:id])
#redirect_to #user
end
end
and my routes.rb
Estaciones::Application.routes.draw do
root :to => "static_pages#home"
match '/contact', :to=>'static_pages#contact'
match '/about', :to=>'static_pages#about'
devise_for :users
resources :users do
resources :cars
end
my rake routes:
root / static_pages#home
contact /contact(.:format) static_pages#contact
about /about(.:format) static_pages#about
new_user_session GET /users/sign_in(.:format) devise/sessions#new
user_session POST /users/sign_in(.:format) devise/sessions#create
destroy_user_session DELETE /users/sign_out(.:format) devise/sessions#destroy
user_password POST /users/password(.:format) devise/passwords#create
new_user_password GET /users/password/new(.:format) devise/passwords#new
edit_user_password GET /users/password/edit(.:format) devise/passwords#edit
PUT /users/password(.:format) devise/passwords#update
cancel_user_registration GET /users/cancel(.:format) devise/registrations#cancel
user_registration POST /users(.:format) devise/registrations#create
new_user_registration GET /users/sign_up(.:format) devise/registrations#new
edit_user_registration GET /users/edit(.:format) devise/registrations#edit
PUT /users(.:format) devise/registrations#update
DELETE /users(.:format) devise/registrations#destroy
user_cars GET /users/:user_id/cars(.:format) cars#index
POST /users/:user_id/cars(.:format) cars#create
new_user_car GET /users/:user_id/cars/new(.:format) cars#new
edit_user_car GET /users/:user_id/cars/:id/edit(.:format) cars#edit
user_car GET /users/:user_id/cars/:id(.:format) cars#show
PUT /users/:user_id/cars/:id(.:format) cars#update
DELETE /users/:user_id/cars/:id(.:format) cars#destroy
users GET /users(.:format) users#index
POST /users(.:format) users#create
new_user GET /users/new(.:format) users#new
edit_user GET /users/:id/edit(.:format) users#edit
user GET /users/:id(.:format) users#show
PUT /users/:id(.:format) users#update
DELETE /users/:id(.:format) users#destroy
this is the new.html.erb for new cars
<div class="container">
<h2>new car registration</h2>
<%= form_for(:users, :url => user_car_path(current_user)) do |f| %>
<div><%= f.label :brand %><br />
<%= f.text_field :brand %></div>
<div><%= f.label :color %><br />
<%= f.text_field :color %></div>
<div><%= f.label :model %><br />
<%= f.text_field :model %></div>
<div><%= f.label :year %><br />
<%= f.text_field :year %></div>
<div><%= f.submit "new car",:class => "btn btn-primary" %></div>
<% end %>

Answer 1

<%= link_to "new car", new_user_car_path(current_user)%>
should be ok given your route
new_user_car GET /users/:user_id/cars/new(.:format) cars#new
but the error says that a car#show (not new!) is missing, so maybe look for that.
When is the error exactly thrown?
ADDITION: now that you've posted the form,
I think the line producing the error is
<%= form_for(:users, :url => user_car_path(current_user)) do |f| %>
because user_car_path needs both a user and a car - so you would need
user_car_path(current_user,#car)
I've used just this in my form:
<%= form_for ([#user,#car]) do |f| %>
but the bottom line is, every time you're referencing a car, you need also the enclosing user reference.

Answer 2

I don't know if it is generating the problem, but why are you passin the current_user here:
<%= link_to "new car", new_user_car_path(current_user)%>
In your creation action, you are already getting the current user:
#car = current_user.Car.new(params[:car])
Also in your show action you have car and not Car
def show
#car = current_user.car.find(params[:id])
EDIT - based in your routes, I can see you have a nested resource:
your cars controller should be:
class CarsController < ApplicationController
def new
#user = User.find(params[:user_id])
#car = #user.cars.build
end
def create
#user = User.find(params[:user_id])
#car = #user.cars.build(params[:car])
if #car.save
flash[:notice] = "new car created success"
#redirect_to current_user, :flash => { :success => "car created!" }
else
#redirect_to new_user_car_path,
flash[:notice] = "sorry try again"
end
end
def index
#car=Car.all
end
...
And the link to create the new car is new_user_car_path

Answer 3

For what it's worth, I had a problem very similar to the one described by OP: the "index" action for my controller worked, but the "new" action threw the same exception ("show" route missing, which was not the case). It turned out Rails had some problem with the pluralization of my model name (ending in a 'y').
Rather than fighting the convention, I ended up choosing another model name with simpler pluralization and things were fine.