I have discovered that if I build the book’s source code for both the stateless and stateful component sections of the book, errors occur when running the application. Specifically, when clicking on either “show” or “edit” in the /products page, the following error occurs:
protocol Ecto.Queryable not implemented for %Pento.Catalog.Product{__meta__: #Ecto.Schema.Metadata<:loaded, "products">, description: "Help king kong get past the donkeys.", id: 1, inserted_at: ~N[2021-12-01 17:22:31], name: "Donkey Kong", ratings: #Ecto.Association.NotLoaded<association :ratings is not loaded>, sku: 5555555, unit_price: 5.0, updated_at: ~N[2021-12-01 17:22:31]} of type Pento.Catalog.Product (a struct). This protocol is implemented for the following type(s): BitString, Tuple, Ecto.Query, Atom, Ecto.SubQuery