In the context of la_facebook, callbacks are a subclass of la_facebook.callbacks.base.BaseFacebookCallback.

The callback is called after the user authenticates with Facebook, either for the first time, or when returning after authentication expiration. The callback determines what happens next, whether that be a user being created, or the browser being redirected.

la_facebook ships with two callbacks. BaseFacebookCallback defines the key steps that any response to a facebook auth should include, but is largely an abstract class. DefaultFacebookCallback is a working callback that addresses the most common use case for basic user auth. Most projects will probably be fine to just use this default implementation.

What the default implementation does

When a new user comes to your site, and clicks on a link that calls the la_facebook.views.facebook_login view, they are redirected to facebook where they are authenticated and approve your app. They are then redirected to your site and the default callback is executed. This callback fist checks whether there is already an authenticated Django user in the session. If not the Facebook id of the user is examined and it is determined whether they have previously authenticated to the site by looking for database model that stores an association between a Django user and a Facebook user.

If there exists a prior association, the expiration of that users Facebook authentication token is updated, the Django session expiration is set to match, and the user is logged and redirected.

If no prior association is present, a django user and its association object are created. The default Django username consists of the facebook user’s name sluggified and concatenated with their facebook id. Any profile object, as defined in Django’s settings, is updated with any matching fields in the users Facebook data.

Callback Reference

A callback is a view like object is called with instances of a Django request, OAuthAccess, and OAuth20Token.

class BaseFacebookCallback

Provides a largely abstract class defining an auth interaction with Facebook.

__call__(request, access, token)

is called by the view and handles the basic check of whether the user is authenticated and dispatches to the other methods as nessasary and then returns the response to the view and thus to the browser (usually a redirect)

fetch_user_data(request, access, token)

Not implemented.

lookup_user(request, access, token)

Not implemented.

redirect_url(request, access, token)

Checks in order: the request GET params, the session, settings for a url to redirect to.

handle_no_user(request, access, token, user_data)

Not implemented.

handle_unauthenticated_user(request, access, token, user_data)

Not implemented.


Concatenates a sluggified facebook name and user id

class la_facebook.callbacks.default.DefaultFacebookCallback

Provides the default implementation.

fetch_user_data(self, request, access, token):

Uses the authorized token and makes an API call to Facebook to retrieve the user graph data.

lookup_user(self, request, access, user_data):

Based on the Facebook user ID in the :param user_data:, will attempt to lookup a an associated Django user. If one is not found, returns None.

persist(self, user, token, user_data):

Creates or updates the user association object, and if available updates the Django user’s email from the Facebook user’s data.

handle_no_user(self, request, access, token, user_data):

The default implementation simply returns create_user().

login_user(self, request, user):

The default implementation assumes Django’s model backend, and will log the user in via that backend’s login method.

handle_unauthenticated_user(self, request, user, access, token, user_data):

Given a valid user, the user is first logged in, and then their Facebook data is created or updated through persist. Finally the session’s expiration is set to match the expiration of the Facebook auth token.

update_profile_from_graph(self, request, access, token, profile):

Given a profile object, will try to update any fields whose names match the Facebook usergraph object.

create_profile(self, request, access, token, user):

if AUTH_PROFILE_MODULE is set, will attempt to create and then update a profile object for the given user.

create_user(self, request, access, token, user_data):

If the user does not already exist, creates a user, a profile if available, and logs the user in.