Rails Relationships Group Lab

Discuss

Answer these questions to the satisfaction of everyone in the group:

Rails favors convention over configuration, what do you think this means?
The way we have learned migrations, there is an intermediate step between generating a migration and running that migration. What is it and why does that step exist?
What does running a migration do?
What is a foreign key used for?
What is ActiveRecord exactly?

Build together

You'll have plenty of opportunity to do Rails stuff on your own (like Project 4). For now, build something together. Each person should have completed the step before the group moves on to the next step.

Answer any questions amongst yourselves along the way, before moving on to the next step.

1. Initialize new project

In student_labs make a project called afternoon_lab_app_api. Remember rails new, the --api flag, and the -d postgresql flag.

2. Create the postgres database

rails db:create

3. Generate a migration to create a table for `products`

Do not fill in the migration file yet.

4. Generate a migration to create a table for `reviews`

Do not fill in the migration file yet.

Eventually, products and reviews will have a one-to-many relationship. A product will have many reviews. A review will belong a product.

5. Fill in the migration file for `products`

A product should have a title and a price. Research how to use a number as a datatype.

Do not run the migration yet.

6. Fill in the migration file for `reviews`

A review should have a rating (number) and content (string)

Do not run the migration yet.

7. Migrate both migration files

rails db:migrate will migrate all migration files that have not yet been migrated. Both the products and reviews tables should be created when you run the migration.

Check in the schema.rb.

8. Make a model for Product and a model for Review

Create product.rb and review.rb.

These models should be Classes that inherit from ApplicationRecord.

Don't add the relations just yet.

9. Test your models in Rails Console

rails c

Perform ActiveRecord queries on Product and Review to make sure they are working. Product.count should be zero.

10. Add a foreign key to reviews

Generate a migration that will add a column to the review schema.

Fill in the migration file: the column should be called product_id and will be a number (an integer).

Run the migrations (finally).

11. Add relationships to the models

Change product.rb to reflect that a Product has many reviews.

Change review.rb to reflect that a Review belongs to a product.

12. Seed some data

In seed.rb, create two products. Do not run the seed yet.

In seed.rb create three reviews. Associate two reviews with a product, and the remaining review with the other product.

Associate them using the expected ids of the seeded products.

Seed the products and reviews. rails db:seed

13. Test the seed in rails console