Feb 18, 2010

User profiles with inheritance in Django

Vladimir Sidorenko

Usually users' profiles are stored in single model. When there are multiple user types, separation is made by some field like user_type.

Situation is a little more complicated when different data is needed for each user type.

Of course it's better when all users have same type and are granted different permissions. But since we got task to have separate user types - we'll have to solve it.

Simple solution

The most obvious solution is to make base profile with type identifier, which will pull needed model instance:

false

But I don't really like this solution. Firstly, get_final_profile method is basically a big switch-case. Secondly - we must not forget to call extra method.

I wanted to simply write request.user.profile ans get needed profile instance. This is possible by combining two known tricks - Upcast and AutoOneToOneField.

Upcast

Allows to get sublass instance from base class instance.

AutoOneToOneField

Allows creating related objects on request. This field is not needed per se, only idea. Taking AutoOneToOneField as a base, it's easy to create a new one that calls upcast when related objects is requested.

Solution

false

Now profile looks like this:

false

In order to get users, profile, we just need to write requst.user.profile.

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