Oscar design decisions

The central aim of Oscar is to provide a solid core of an e-commerce project that can be extended and customised to suit the domain at hand. This is achieved in several ways:

Core models are abstract

Online shops can vary wildly, selling everything from turnips to concert tickets. Trying to define a set of Django models capable for modeling all such scenarios is impossible - customisation is what matters.

One way to model your domain is to have enormous models that have fields for every possible variation; however, this is unwieldy and ugly.

Another is to use the Entity-Attribute-Value pattern to use add meta-data for each of your models. However this is again ugly and mixes meta-data and data in your database (it’s an SQL anti-pattern).

Oscar’s approach to this problem is to have minimal but abstract models where all the fields are meaningful within any e-commerce domain. Oscar then provides a mechanism for subclassing these models within your application so domain-specific fields can be added.

Specifically, in many of Oscar’s apps, there is an abstract_models.py module which defines these abstract classes. There is also an accompanying models.py which provides an empty but concrete implementation of each abstract model.

Classes are loaded dynamically

The complexity of scenarios doesn’t stop with Django models; core parts of Oscar need to be as customisable as possible. Hence almost all classes (including views) are dynamically loaded, which results in a maintainable approach to customising behaviour.

URLs and permissions for apps are handled by Application instances

The oscar.core.application.Application class handles mapping URLs to views and permissions at an per-app level. This makes Oscar’s apps more modular, and makes it easy to customise this mapping as they can be overridden just like any other class in Oscar.

Templates can be overridden

This is a common technique relying on the fact that the template loader can be configured to look in your project first for templates, before it uses the defaults from Oscar.