Agile Web Development with Rails 6

Iteration E1: Creating a Smarter Cart

Associating a count with each product in our cart is going to require us to modify the line_items table. We’ve used migrations before; for example, we used a migration in ​Applying the Migration​, to update the schema of the database. While that was as part of creating the initial scaffolding for a model, the basic approach is the same:

depot> bin/rails generate migration add_quantity_to_line_items quantity:integer

Rails can tell from the name of the migration that you’re adding columns to the line_items table and can pick up the names and data types for each column from the last argument. The two patterns that Rails matches on are AddXXXToTABLE and RemoveXXXFromTABLE, where the ...