Rails - dynamic routes inside an each block - ruby-on-rails

Question

This is my first rails project and I'm a complete newbie to all code, not just Ruby, so please forgive me if I don't explain my issue concisely.
I have a model, Car, which belongs to another model, User. I want my Cars index page to show all cars in the database, so I made a custom route of '/cars/', rather than the :user_id/cars/:id route generated by Rails.
The Car info is getting output onto my index page, but I can't work out how to generate links back to the Car show page.
I'm sure it's something simple, but I've been reading the Rails Guide and other questions on here all day and haven't fixed it yet.
Here's the block:
<% #cars.each do |car| %>
<li>
<div class="well row <%= cycle('', 'white-bg') %>">
<div class="col-sm-4 text-center">
<!-- thumbnail for car here -->
</div>
<div class="pull-left">
<%= link_to car.id, user_car_path(#user, car) do %>
<h3><%= car.year %> <%=car.make %> <%= car.model %></h3>
<% end %>
</div>
<div>
<h3 class="pull-right"><%= car.price %></h3>
</div>
</div>
</li>
<% end %>
Routes:
get 'cars' => 'cars#index', as: :cars
resources :users do
resource :profile
resources :cars, except: :index
end
end
Controller:
def new
#user = User.find( params[:user_id] )
#car = #user.cars.build
end
# POST request to /users/:user_id/cars
def create
#user = User.find( params[:user_id] )
#car = #user.cars.build( car_params )
if #car.save
redirect_to user_path( params[:user_id] )
end
end
# GET request to /users/:user_id/cars/:id
def show
#user = User.find( params[:user_id] )
#car = #user.cars.find( params[:id] )
end
# GET request to /cars/
def index
#cars = Car.all
end
The error is:
No route matches {:action=>"show", :controller=>"cars", :id=>"1", :user_id=>nil} missing required keys: [:user_id]
I'm guessing I'm missing something in the controller, but everything I've tried in there just generates other errors.
Thanks!
cars_path GET /cars(.:format) cars#index
POST /cars(.:format) cars#create
new_car_path GET /cars/new(.:format) cars#new
edit_car_path GET /cars/:id/edit(.:format) cars#edit
car_path GET /cars/:id(.:format) cars#show
PATCH /cars/:id(.:format) cars#update
PUT /cars/:id(.:format) cars#update
DELETE /cars/:id(.:format) cars#destroy
new_user_profile_path GET /users/:user_id/profile/new(.:format)
profiles#new
edit_user_profile_path GET /users/:user_id/profile/edit(.:format)
profiles#edit
user_profile_path GET /users/:user_id/profile(.:format)
profiles#show
PATCH /users/:user_id/profile(.:format) profiles#update
PUT /users/:user_id/profile(.:format) profiles#update
DELETE /users/:user_id/profile(.:format) profiles#destroy
POST /users/:user_id/profile(.:format) profiles#create
user_cars_path GET /users/:user_id/cars(.:format) cars#index
POST /users/:user_id/cars(.:format) cars#create
new_user_car_path GET /users/:user_id/cars/new(.:format) cars#new
GET /cars/:id/edit(.:format) cars#edit
GET /cars/:id(.:format) cars#show
PATCH /cars/:id(.:format) cars#update
PUT /cars/:id(.:format) cars#update
DELETE /cars/:id(.:format) cars#destroy

Answer 1

I would suggest an alternative solution where you "unnest" the cars resource - and just provide a index route for the cars belonging to a certain user:
# routes.rb
resources :cars
resources :users do
resources :cars, module: 'users', only: [:index]
end
# app/controller/cars_controller.rb
class CarsController < ApplicationController
# GET /cars
def index
#cars = Car.all
end
# show, create, delete, new...
end
# app/controller/users/cars_controller.rb
class Users::CarsController < ApplicationController
# GET /users/:user_id/cars
def index
#user = User.includes(:cars).find(params[:user_id])
#cars = #user.cars
end
end
Depending on the context you can move more of the collection routes (new, create) to Users::CarsController if you for example are able to create cars for other users. Nesting member routes (that act on a single record)
is seldom necessary. You can avoid it by using the shallow: true option:
resources :users do
resources :cars, shallow: true
end
This lets you route to a car by simply doing:
link_to(#car.name, car_path(#car))
# or
link_to(#car.name, #car)
If you decide to keep your current setup you route to nested resource by using an array or keywords:
link_to(#car.name, user_car_path(user: #user, id: #car))
# or
link_to(#car.name, [#user, #car])