Question

There’s photologue application, simple photo gallery for django, implementing Photo and Gallery objects.
Gallery object has ManyToMany field, which references Photo objects.

I need to be able to get list of all Photos for a given Gallery. Is it possible to add Gallery filter to Photo’s admin page?
If it’s possible, how to do it best?

Answer 1

You need to write a custom FilterSpec! Custom Filter in Django Admin on Django 1.3 or below
It’ll look like this:

from django.contrib.admin.filterspecs import RelatedFilterSpec, FilterSpec
from models import Gallery

class GalleryFilterSpec(RelatedFilterSpec):
    def __init__(self, f, request, params, model, model_admin):
        self.lookup_kwarg = f.name
        self._lookup_model = f.rel.to
        self.lookup_val = request.GET.get(self.lookup_kwarg, None)
        self.user = request.user
        self.lookup_choices = [(g.pk, g.name) for g in Gallery.objects.all()]

    def has_output(self):
        return len(self.lookup_choices) > 1

    def title(self):
        return self._lookup_model._meta.verbose_name

FilterSpec.filter_specs.insert(0, 
        (lambda f: f.rel.to == Gallery, GalleryFilterSpec))

Put it in a module filters.py in your app package and import it in you admin.py (it’s important to import it, so that the filter becomes registered on the admin site!)

EDIT: “f” is the field instance, in this case models.ManyToManyField The last line registers the FilterSpec for all fields that have a relation to the Gallery model. This will not work as you mentioned if the field is defined on the Gallery model, since django.contrib.admin.views.main.ChangeList.get_filters checks if the field you define in the list really exist on the model (doesnt work for related_name either). I think the easiest way around is that you could make a custom template for that changelist and hardcode your filter in there, the FilterSpec itself isn’t need for the filtering itself, django uses just the url get parameters for that!