Nested Resources

Learning Goals

• How do you use nested resources in Rails?
• When should you use Nested Resources?

Warm Up

Create a table containing all 8 http-verbs, URI-patterns, and controller actions that Rails gives you when you have the following:

# config/routes.rb

resources :muffins

Background

Read this section of the Rails routing documentation and discuss with someone close to you.

Examples

GET  /directors/1/movies
GET  /directors/1/movies/new
POST /directors/1/movies

How do we Create Nested Routes?

# config/routes.rb
resources :directors do
  resources :movies
end

• Run rake routes

Shallow Nesting

# config/routes.rb
resources :directors shallow: true do
  resources :movies
end

• Run rake routes again.
• How does this differ from what was generated without shallow: true?

form_for Arguments

form_for uses the object it receives as an argument to determine:

• Whether to render a new form or an update form
• Whether the fields in the form correspond to attributes on the object
• What route to use when sending the information when a user hits submit

form_for with Nested Resources

• Need to pass both the existing director and new movie
• Will provide them in an array as an argument
• Need to update both our controller and our view

Let’s code along:

• You should have a test already to see the form for a new movie. Now let’s create a new movie with a director. Based on what we know about nested routes, let’s start here:

  #spec/features/user_can_create_a_new_movie_spec.rb
  director = Director.create(name: "Ilana")
  visit "/directors/#{director.id}/movies/new"

  fill_in :title, with: "Finding Nemo"
  fill_in :description, with: "A sad fish story"

  click_on "Create Movie"

  expect(current_path).to eq("/movies/#{Movie.last.id}")
  expect(page).to have_content("Finding Nemo")
  expect(page).to have_content("A sad fish story")
  expect(page).to have_content(director.name)

• What is in your controller? What is in your view?

• Last week, we wrote a test to see a new form for a new movie but did not create a new movie.

• Our controller should look like this:

#app/controllers/movies_controller.rb
def new
end

• And our view like this:

<form action="/movies" method="post">
  <input type="text" name="movie[title]" value="Title">
  <input type="text" name="movie[description]" value="Description">
  <input type="submit" value="Create Movie">
</form>

• This should take us all the way to a failing test:

Failure/Error: click_on "Create Movie"

     ActionController::RoutingError:
       No route matches [POST] "/movies"

• Hmmmm, but we have opened the routes for making a new movie for a director. Let’s check out rake routes output to see what route we are actually trying to hit. What are we looking for? A route that creates our new movie. What HTTP verb do we use when we create a new resource?

  POST   /directors/:director_id/movies(.:format)     movies#create

• Based on the route above, we need our form to post to a specific directors movies. How can we do that? Through the controller and form! Let’s make those adjustments.

# app/controllers/movies_controller.rb
def new
  @director = Director.find(params[:director_id])
  @movie    = Movie.new
end

• Lets update our view for the movie to use the form_helper that rails gives us to build a form.

# app/views/movies/new.html.erb
<h1>Create a New Movie</h1>

<%= form_for [@director, @movie] do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title %>
  <%= f.label :description %>
  <%= f.text_area :title %>
  <%= f.submit %>
<% end %>

Let’s run RSpec and adjust our Movies Controller to point the form to create

def create
  director = Director.find(params[:director_id])
  movie = director.movies.create(movie_params)
  redirect_to "/movies/#{movie.id}"
end

• LAST: Adjust your view to show the director of the movie!
• We should have a passing test!!!

Creating a New Movie via localhost

• Be sure you have at least one director in your database
• Run rails s
• Visit /directors/1/movies/new

Mixing Nested and Non-Nested Routes

• What if we want to see a list of all movies?

# config/routes.rb
resources :directors, shallow: true do
  resources :movies
end

resources :movies, only: [:index]

Visit /movies and you should see all movies.

Checks for Understanding

Turn and talk to your neighbor and discuss:

• When would you use a nested resource?
• How do you nest a resource in your routes file?
• How does that change your routes?
• What does it mean to use shallow nesting? Why would you do this?
• What changes do you need to make in your controller when you nest a resource?