On Fri, Aug 22, 2008 at 3:24 AM, Benjamin Buch <[EMAIL PROTECTED]> wrote:
>
>
>
> > I'm not sure i understand you question. You can filter via the
> > attributes of a related object like this:
> > Recording.objects.filter(song__artist="Ben Folds")
>
> Yes, and that's perfectly all right when you are only interested only
> in the related objects.
> But what do you do when you want to do something like:
>
> "Give my all songs that start with the letter R AND limit the related
> recording_set to the recordings that have represents_song=True"?
>
> You could do this with two queries:
> songs = Song.objects.filter(title__startswith='R')
> recordings = Recording.objects.filter(represents_song=True)
>
> But then there would be no connection between songs and recordings.
> Every song in songs would still have attached all recordings that
> belong to the song, not only the recordings with represents_song=True.
>
> What I want is to filter objects and at the same time the FOO_sets of
> the single objects.
> When I understand this right, with filters you can either filter the
> objects itself OR you can filter the related objects, but not both at
> the same time.
>
> I think this can only be don via a custom manager or a custom method.
>
> As I don't understand how custom managers work yet to well, I tried it
> with a custom method:
>
> class Song(models.Model):
> title = models.CharField(max_length=50)
> description = models.TextField(blank=True)
>
> def __unicode__(self):
> return self.title
>
> def get_representative_recording(self):
> representative_recording =
> self.recording_set.get(represents_song=True)
> return representative_recording
>
> class Recording(models.Model):
> song = models.ForeignKey(Song)
> mp3 = models.FileField(upload_to='songs')
> represents_song = models.BooleanField()
>
> I can now filter the songs in the view:
>
> songs = Song.objects.filter(filter_for_whatever_you_like_here)
>
> And access the "representative recording" like this in the template:
>
> {{ song.get_representative_recording.mp3.url }}
>
> I can't see how this could be done only by filtering, without a custom
> method or a custom manager.
>
> -benjamin
>
How about:
songs = Recording.objects.filter(song__title__startswith='R',
represents_song=True)
http://www.djangoproject.com/documentation/db-api/#filter-kwargs
"Multiple parameters are joined via AND in the underlying SQL statement."
- Garrett
>
>
>
> >
>
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