In the Classes section, you declare an Order class as follows:
class Order < ActiveRecord::Base
But at the end of the paragraph, you state "This Order class is defined to be a subclass of the ApplicationRecord class. I’m presuming you mean “… ActiveRecord class”.
I see later (tipped off to look further by the code at the bottom of page 83), while working through the Depot project that we have:
/app/models/application_record.vb
class ApplicationRecord < ActiveRecord::Base
primary_abstract_class
end
and then:
/app/models/product.rb
class Product < ApplicationRecord
end
So I’m guessing that this eventual set up is where that initial ApplicationRecord came from.