1. Open the User class (app/models/user.rb) in your text editor.

   Using the Book class as an example, update User so a user has many reviews.

1. What do your changes look like? You should have added the following line to User:

   has_many :reviews
   

2. If you didn’t already, make this change to User.

3. Save your changes.

Now that we’ve defined a relationship between users and reviews, let’s see what we can do with it on the rails console.

1. Open Terminal, make sure you’re in the bookstore directory, and start the rails console.

2. Find your first user and assign it to a variable called my_first_user.

3. Now, try running my_first_user.reviews.

   Yikes! That looks like a gnarly error… 😅

   The ActiveRecord::StatementInvalid error is giving you hint to what’s going on. Burried inside the error, you have this message:

   no such column: reviews.user_id
   

   We’ve defined the relationship between users and reviews on the model level, but we haven’t defined it on the database level.

   Since we said a user can have many reviews, Rails is expecting the reviews table to have a user_id column. Let’s add it!

4. Before you continue, exit the rails console.

To add a user_id column to the reviews table, we’ll need to create a new migration.

1. In Terminal, run the following command:

   rails generate migration add_user_id_to_reviews
   

   This will generate a new timestamped migration file named AddUserIdtoReviews. It’s filename will be something along the lines of db/migrate/TIMESTAMP_add_user_id_to_reviews.rb

1. The AddUserIdtoReviews migration will be very similiar to another migration you’ve created. Can you think of which one?

   AddUserIdtoReviews is gonna look a lot like AddBookIdToReviews.

   class AddBookIdToReviews < ActiveRecord::Migration[5.0]
     def change
       add_column :reviews, :book_id, :integer
     end
   end
   

   You added a book_id column to the reviews table because you wanted to define the relationship between books and reviews on the database level. Remember, a book can have many reviews.

   We want to do the same thing in AddUserIdtoReviews, except we’re adding a user_id to reviews.

2. Using this as an example, update the change method of the AddUserIdtoReviews migration to add a user_id column to the reviews table. The user_id column should be an integer column.

1. What does your change look like? You should’ve added the following line to the change method:

   add_column :reviews, :user_id, :integer
   

2. If you didn’t already, add this line, save your changes, and run the migration.

Now that we’ve defined the relationship between users and reviews on both the model and the database levels, we can go back to exploring the relationship on the rails console.

1. Go to Terminal and start the rails console.

2. Assign your first user to a variable called my_first_user.

3. Now, try running my_first_user.reviews.

   You get an empty collection because my_first_user doesn’t have any reviews. Let’s change that!

1. Assign your first book to a variable called my_first_book.

2. Now, run the following code to create a new review for my_first_book that will also be associated with my_first_user.

   my_first_book.reviews.create(body: "This review was written by a user!", user_id: my_first_user.id)
   

   On the new review, we’re setting a body and a user_id.

   By setting the user_id to my_first_user’s id, we’ll know that the review belongs to my_first_user.

1. Now that my_first_user has a review, try running my_first_user.reviews again.

   I thought my_first_user would have reviews 😔

   But my_first_user does have reviews!

2. Do you remember when you assigned the first user in your database to my_first_user?

   my_first_user = User.first
   

   It’s been a while - it was the first thing you did when you entered the rails console.

   my_first_user is a variable, and it only knows about the data that existed when it was defined. Even though your first user now has a review in the database, the variable my_first_user doesn’t know anything about it.

3. To update my_first_user with the new review data, run:

   my_first_user.reload
   

4. Now, try running my_first_user.reviews.

   🎉

Let’s take a closer look at that new review.

1. Run the following code to assign the new review to a variable called my_last_review:

   my_last_review = Review.last
   

2. my_last_review should have a user_id. Try running my_last_review.user_id.

   This will return the user_id of the user who’s associated to my_last_review. Since we set it to my_first_user’s id, it will most likely be 1.

3. Now, let’s try to get the user from the review. Try running my_last_review.user.

   Hmm…that’s an interesting error. Any thoughts on why you got a NoMethodError.

   (The hint is in the error)

   You got a NoMethodError because we haven’t completely defined the relationship between users and reviews. You defined part of the relationship - a user has many reviews. However, you haven’t defined the relationship between reviews and users.

We need to define the relationship between reviews and users - a review belongs to a user.

1. Open app/models/reviews.rb. You might notice another relationship we already defined 😉

   Since a review also belongs to a book, you previously added this line:

   belongs_to :book
   

   Now, we need to do the same thing for users.

2. Update Review so a review belongs_to a user.

That probably sounded more challenging than it was 😅

1. You should’ve added this line

   belongs_to :user
   

2. If you didn’t already, add this line to Review and save your changes.

Now, let’s see if we can’t get your last review’s user.

1. Go back to the rails console and run the following line to pull in your changes.

   reload!
   

2. Get your last review again and assign it to my_last_review.

3. Now, try running my_last_review.user.

4. Yayay!!!

   

5. Exit the rails console.

1. In the ReviewsController, change the review_params method from

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

   to

   def review_params
     permitted_params = params.require(:review).permit(:body)
     permitted_params.merge(user_id: session[:user_id])
   end
   

   We’re still using strong parameters to restrict which form fields can get set on a new review, but we’ll assign them to a new variable called permitted_params.

   Then, we’ll use the merge method to add user_id to permitted_params.

   user_id will be set to session[:user_id].

2. Save your changes and start your application’s web server.

3. Now, login and write a new book review!

1. Did you write a really inspiring review?? 😉

   Let’s take a look at it on the rails console.

2. Stop your application’s web server and start the rails console.

3. Now, get your last review and assign it to a variable called my_last_review.

4. Let’s see who write your last review…

   Run my_last_review.user.

   Yay! I hope “CatPower” left a good review 😝

5. Exit the rails console and restart your application’s web server.

1. Do you remember where reviews are shown?

   In your text editor, open app/views/books/show.html.erb.

2. Towards the end of the template, you’re showing all of a books reviews in an unordered list. Let’s include review usernames in the unordered list.

   Change the reviews unordered list from

   <ul>
     <% @book.reviews.each do |review| %>
       <li> <%= review.body %> </li>
     <% end %>
   </ul>
   

   to

   <ul>
     <% @book.reviews.each do |review| %>
       <% if(review.user.present?) %>
         <li> <%= review.user.username %> - <%= review.body %> </li>
       <% else %>
         <li> Anonymous - <%= review.body %> </li>
       <% end %>
     <% end %>
   </ul>
   

   We’ll show the usernames for reviews who have users. However, you probably have some older reviews in your database that don’t have users. When that happens, we’ll show “Anonymous” instead.

3. Save your changes and visit a book with reviews. You should see a mix of anonymous and not so anonymous users that have left behind some reviews 😊

4. Try adding new reviews. If you’re still logged in as “CatPower”, she’ll start getting a lot of reviews in her name…

5. When you’re done, stop your application’s web server.