On Wed, 2009-03-25 at 20:38 -0700, adrian wrote: > > I have a Sighting model which has a foreign key field "notes" to a > model called Notes. > Notes has a predefined empty note with id=1. If the user specifies > no note then > I want the sighting to reference this predefined empty note. > So in my view: > > note = form.cleaned_data['notes'] > if note != "": # notes field not blank, save note to db > notes_object = Notes(notes=note) > notes_object.save() > else: #get blank note instance > notes_queryset = Notes.objects.get( > id__exact=1 > ) > notes_object = notes_queryset[0] > > sighting = Sighting( > #more fields here > notes = notes_object, > #more fields > ) > > I have two questions about this. > > First, sometimes I'm getting an error: > TypeError: 'Notes' object is unindexable (on the line with > notes_queryset[0] ) > Am I doing this right? The Notes with id=1 is definitely present in > the database. > I thought a queryset always returned a list of model instance objects > (in this case a list of 1).
There are a bunch of queryset methods that do not return a queryset. They return something else. The get() method is one of those: it returns an object. So, in fact, *every* time you hit that line you will see the error, since Notes.objects.get(id=1) returns a Note object, not a queryset. The methods for querysets are divided into two sections in the documentation, along those lines (returns a queryset or doesn't). get() leads off this section: http://docs.djangoproject.com/en/dev/ref/models/querysets/#queryset-methods-that-do-not-return-querysets > Second, when the note is empty, is there a way to avoid querying the > database to create the instance of Notes? Since I already know the id > and all the contents, the query gives no new information. Just > curious, not a big performance hit! For each foreign key attribute, there is a hidden attribute that stores the actual data value (as opposed to the reference to the other model). Normally, it will have the same name as the attribute with "_id" appended. So you can assign the pk value of the default Note to that: sighting = Sighting(..., notes_id=1, ....) ... assuming your default version has pk of "1" -- adjust to taste. This is slightly internal API, so I don't think it's documented anywhere. But it works. Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
