Django MTMField: limit_choices_to = other_ForeignKeyField_on_same_model?

Question

I have a couple of django models that look like this:

from django.contrib.sites.models import Site class Photo(models.Model): title = models.CharField(max_length=100) site = models.ForeignKey(Site) file = models.ImageField(upload_to=get_site_profile_path) def __unicode__(self): return self.title class Gallery(models.Model): name = models.CharField(max_length=40) site = models.ForeignKey(Site) photos = models.ManyToManyField(Photo, limit_choices_to = {'site':name} ) def __unicode__(self): return self.name 

I have all kinds of entertainments that try to make limit_choices_to work with the Gallery model. I just want the administrator to show options for photos belonging to the same site as this gallery. Is it possible?

Answer 1

I would remove the site field in my Photo model and add ForeignKey to Gallery . I would remove limit_choices_to from the photos fields in Gallery .

Since you are using ForeignKey to site s, this means that sites do not exchange galleries and photos. Therefore, the presence of those that I mentioned above is already useless.

 class Photo(models.Model): title = models.CharField(max_length=100) gallery = models.ForeignKey(Gallery, related_name='photos') file = models.ImageField(upload_to=get_site_profile_path) def __unicode__(self): return self.title class Gallery(models.Model): name = models.CharField(max_length=40) site = models.ForeignKey(Site) def __unicode__(self): return self.name 

Once you set a site in the gallery, all of its photos inherit this property. And the site will be available as photo_instance.gallery.site :

 @property def site(self): return self.gallery.site 

This should work as if you had a site field. But I did not test it.

Changes or course if you decide that a gallery or photo can appear on several sites.

Answer 2

Yes. You need to redefine the form that the administrator uses for the Gallery model, and then limit the set of requests in the photos field in this form:

 class GalleryAdminForm(django.forms.ModelForm): class Meta: model = Gallery def __init__(self, *args, **kwargs): super(GalleryAdminForm, self).__init__(*args, **kwargs) self.fields['segments'].queryset = Photo.objects.filter(site=self.instance.site) class GalleryAdmin(django.contrib.admin.ModelAdmin): form = GalleryAdminForm django.contrib.admin.site.register(Gallery, GalleryAdmin) 

Answer 3

According to docs , limit_choices_to does not work when used on ManyToManyField with a staging table. "In my reading, this means that it has no effect, because ManyToManyFields use staging tables ...

I did not try to make it work on the Admin site, but from your own views you can create a form and override the set of queries used to fill out the list of options:

 form.fields["photos"].queryset = request.user.photo_set.all()