1. Let’s start by taking a look at your application’s routes file. In your text editor, open config/routes.rb.

   So far, you’ve specified one resource in your routes file - books.

   resources :books
   

   It’s been a while since we’ve been inside the routes file, but your application now has a new resource - reviews. You’ve defined a relationship between these two resources in your application. A book can have many reviews, and review belongs to a book.

   We can define this relationship in your routes file.

2. In your routes file, change

   resources :books
   

   to

   resources :books do
     resources :reviews
   end
   

3. Save your changes.

Let’s see how that changed your application’s routes.

1. Open Terminal, go to the bookstore directory, and run rake routes.

   Whoa! Your application’s routing table got waaaaay bigger.

   Your application now has a bunch of review routes. Do you notice a pattern in their paths?

   /books/:book_id/reviews
   /books/:book_id/reviews
   /books/:book_id/reviews/new
   

   They all start with /books/:book_id because of the change you made to your application’s routes file:

   resources :books do
     resources :reviews
   end
   

   By nesting :reviews inside of :books, you’re setting up all your review routes to go through the book they belong to.

   For example, instead of having a route to get all your application’s reviews (/reviews), you have a route to get all of a books reviews (/books/:book_id/reviews).

   Why are we doing this again?

   We’re setting up your application’s routes to reflect the belongs_to/has_many relationship that exists between books and reviews.

   It might feel a little abstract, but this will come in handy when we’re adding reviews.

1. Start your application’s web server, and go to http://localhost:3000/books/1/reviews/new. Since the path starts with /books/1, this is where we’d go to add a review for your first book.

   Those errors sure do get old, don’t they…

1. Go back to Terminal, stop your application’s web server, and run the following command:

   touch app/controllers/reviews_controller.rb
   

   This will create an empty file named app/controllers/reviews_controller.rb.

2. Restart your application’s web server, and open app/controllers/reviews_controller.rb in your text editor.

1. Now you have a file for the ReviewsController, but you still haven’t defined it.

2. Add the following code to app/controllers/reviews_controller.rb

   class ReviewsController < ApplicationController
   end
   

3. Save your changes and revisit http://localhost:3000/books/1/reviews/new.

1. Add an empty new method to the ReviewsController.

   def new
   end
   

2. Save your changes and revisit http://localhost:3000/books/1/reviews/new.

1. First, go back to Terminal and stop your application’s web server.

2. Now, you’ll need to create directory for the review templates. Run the following command:

   mkdir app/views/reviews
   

   This created an empty reviews directory inside of app/views.

3. Then, you can create the new reviews template with the following command:

   touch app/views/reviews/new.html.erb
   

4. Restart your application’s web server, and try going back to http://localhost:3000/books/1/reviews/new.

   What do you think will happen?

   

Let’s get started by showing the title of the book that’s being reviewed at the top of the page.

1. Open the ReviewsController in your text editor, and add the following code to new method.

   @book = Book.find(params[:book_id])
   

   This will make the book’s data available in the new review template.

2. Save your changes.

1. Now, open app/views/reviews/new.html.erb and add the following line:

   <h1> New review for <%= @book.title %> </h1>
   

2. Save your changes and revisit http://localhost:3000/books/1/reviews/new.

   The top of the page should have a message that says “New review for why’s (poignant) Guide to Ruby”.

3. Try visiting the new review path for different books in your bookstore.

   For example, to visit the new review path for the second book in your bookstore you would go to http://localhost:3000/books/2/reviews/new.

   As you go to different paths, the message at the top of the page should change to show that book’s title.

Now, we need to make the new review form.

To get started, we’ll update the ReviewsController new method to make a new review available in the new review template.

That’s a lot of new 😅

1. Open the ReviewsController and add the following line at the end of the new method.

   @review = @book.reviews.build
   

   This will create an empty review for the book that we can use in the new review template.

2. Save your changes.

Now, we can build the review form!

1. This form is going to be pretty simmilar to the new book form, but with less fields.

   <%= form_for(@book) do |f| %>
     <ul>
       <li>
         <%= f.label :title %>
         <%= f.text_field :title %>
       </li>
   
       <li>
         <%= f.label :author %>
         <%= f.text_field :author %>
       </li>
   
       <li>
         <%= f.label :price_cents %>
         <%= f.number_field :price_cents %>
       </li>
   
       <li>
         <%= f.label :quantity %>
         <%= f.number_field :quantity %>
       </li>
   
       <li>
         <%= f.label :description %>
         <%= f.text_area :description %>
       </li>
     </ul>
   
     <%= f.submit(class: "button") %>
   <% end %>
   

2. Using the new book form as an example, add a new review form to app/views/reviews/new.html.erb. The only field you need to set on a review is its body.

   When you’re done, try add a review!

   Psst…not to be a downer, but chances are your solution won’t work

1. To make the new review form work, we need to change

   <%= form_for(@review) do |f| %>
   

   to

   <%= form_for([@book, @review]) do |f| %>
   

   With this change, the form will use the book_reviews_path instead of the invalid reviews_path.

2. Your form should now look like this:

   <%= form_for([@book, @review]) do |f| %>
     <ul>
       <li>
         <%= f.label :body %>
         <%= f.text_field :body %>
       </li>
     </ul>
   
     <%= f.submit(class: "button") %>
   <% end %>
   

   Update your form to match this solution.

3. Save your changes and try adding a review to your first book by visiting http://localhost:3000/books/1/reviews/new.

1. Add an empty create method to the ReviewsController.

   def create
   end
   

2. Save your changes and try adding a review for your first book again by visiting http://localhost:3000/books/1/reviews/new.

1. Add the followling lines to the ReviewsController create method:

   book = Book.find(params[:book_id])
   book.reviews.create(params)
   

   First, we find the requested book and assign it to a variable called book. Then, we create a review for the book using the data that was sent with the form. The data is available in the params hash.

2. Save your changes, revisit http://localhost:3000/books/1/reviews/new, and try adding a review one more time.

To fix the ReviewsController create method, we need to specify the attributes that can be set on reviews. There is only one attribute we care about - body.

1. Add the following method to the end of the ReviewsController:

   def review_params
     params.require(:review).permit(:body)
   end
   

   Inside this review_params method, we’re saying the params hash must have a review hash. Inside the review hash, we’ll allow a body attribute to be used on a new review.

2. Do you remember what the params hash looks like? It looks something like this:

   {"utf8"=>"✓", "authenticity_token"=>"JYZD9Lsnb6RbMX7OW/QUXNY6Uzxd0MYZNcDKHKZjAmggVeGwKb6lPkOE60zgptRlquzdhJo9tOU5r7mLthxXog==", "review"=>{"body"=>"Wooooooooo"}, "commit"=>"Create Review", "book_id"=>"1"}
   

   There’s a bunch of stuff in there, but now we’re restricted to only using the body attribute from the review hash.

3. Now we can use review_params inside the create method. Replace

   book.reviews.create(params)
   

   with

   book.reviews.create(review_params)
   

4. Save your changes, revisit http://localhost:3000/books/1/reviews/new, and try adding a review!

Nothing happened…or did it?

1. Go back to your first book’s details page at http://localhost:3000/books/1.

   Notice anything different???

   Your new review!!! 🎉

2. Nothing happens at the end of the ReviewsController create method so it feels like your review wasn’t created. Let’s fix this.

   Add the following line to the end of the ReviewsController create method:

   redirect_to book_path(book)
   

   After a review is added for the book, we’ll redirect to the book details page for the book so we can verify the new review was created.

3. Save your changes, revisit http://localhost:3000/books/1/reviews/new, and watch what happens when you add a new review.

To create a review for a book, you have to know the URL you want to visit. We can make this a little nicer by adding a link to the new review page from the book details pages.

You’ll be able to quickly write a review for the book you’re looking at.

1. Let’s start by looking at your application’s routes. Go to Terminal, stop your application’s web server, and run rake routes.

   Which row has the path we’ve been using to get to the new review page?

   new_book_review GET    /books/:book_id/reviews/new(.:format)      reviews#new
   

   The first column in the row is a prefix. The new review page has a prefix of new_book_review. We’ll use this prefix to build a link to the new review path.

2. Restart your application’s web server.

1. Now, open app/views/books/show.html.erb in your text editor.

2. Find the “Edit book” link.

   <%= link_to("Edit book", edit_book_path(@book), class: "button") %>
   

3. After the link “Edit book” link, add a link to “Add a Review”.

   The link should say “Add a Review”. It should link to the new_book_review_path for @book, and it should have a “button” class so it gets styled like an actionable element.

1. What did you come up with?

   The link should look something like this:

   <%= link_to("Add a Review", new_book_review_path(@book), class: "button") %>
   

2. Update your solution to match this solution.

3. Save your changes, find some books, and review them!

4. When you’re done writing reviews, stop your application’s web server.