So
far we've built a simple product model and simple catalog model. These models are excellent building blocks on which to begin adding new, more sophisticated functionality. As it stands, our catalog model design is unconnected to our products. We could add, as mentioned earlier, a ForeignKey from Product to Catalog. But this would allow for little in the way of organizing within the catalog, other than what we can do with the basic filter(), order_by(), and other ORM methods that Django provides.
Product categories are an extremely common solution to organization problems in web-based stores. Almost all major Internet retailers organize their products this way. It helps them to provide a more structured interface for their users and can give search engine indexers more precise pages to crawl. We'll discuss more about these tactics later, but let's begin by adding categories to the simple model designs that we created earlier.
Even though our Catalog model is relatively...