when authorizing using iOS Facebook SDK how do I differentiate between no network and login dialog cancelled

Question

I make a

self._facebook authorize:kFacebookAppId permissions:self._facebookPermissions delegate:self];

call which opens the Facebook login dialog.

In case there is no network the dialog opens momentarily and fbDidNotLogin method gets called. In case there is network the dialog opens but the same method fbDidNotLogin gets called if the the user pushes the small close button on top right of the dialog.

I would like to alert the user of no network only in the first case. How do I differentiate between the two scenarios?