How Do I Show Django Admin Change List View of foreign key children?

I'm working on an app with a Model hierarchy of Campaign > Category > Account. Ideally, I'd like users to be able to click on a link in the campaign admin list view and go to a URL like "/admin/myapp/campaign/2/accounts/" which will show a Django admin view with all the handy ChangeList amenities but which is filtered to show just the accounts in categories in the specified campaign (ie. Account.object.filter(category__campaign__id = 2)). (Note, categories themselves I'm happy to just be "filters" on this accounts list view).

I can't seem to find any reference to a way to mimic this item-click-goes-to-list-of-foriegn-key-children approach that is common in many other frameworks.

Is it possible? Is there a "better" approach in the django paradigm?

thanks for any help!

Solution

This was an interesting question so I whipped up a sample app to figure it out.

# models.py
from django.db import models

class Campaign(models.Model):
    name = models.CharField(max_length=20)

    def __unicode__(self):
        return unicode(self.name)

class Category(models.Model):
    campaign = models.ForeignKey(Campaign)
    name = models.CharField(max_length=20)

    def __unicode__(self):
        return unicode(self.name)

class Account(models.Model):
    category = models.ForeignKey(Category)
    name = models.CharField(max_length=20)

    def __unicode__(self):
        return unicode(self.name)

# admin.py
from django.contrib import admin
from models import Campaign, Category, Account

class CampaignAdmin(admin.ModelAdmin):
    list_display = ('name', 'related_accounts', )

    def related_accounts(self, obj):
        from django.core import urlresolvers
        url = urlresolvers.reverse("admin:<yourapp>_account_changelist")
        lookup = u"category__campaign__exact"
        text = u"View Accounts"
        return u"<a href='%s?%s=%d'>%s</a>" % (url, lookup, obj.pk, text)
    related_accounts.allow_tags = True
admin.site.register(Campaign, CampaignAdmin)
admin.site.register(Category)

class AccountAdmin(admin.ModelAdmin):
    list_display = ('category', 'name')
    list_filter = ('category__campaign',)
admin.site.register(Account, AccountAdmin)

You'll need to replace with the name of your app where the Account ModelAdmin lives.

Note: the list_filter on the AccountAdmin is required since Django 1.2.4, Django 1.1.3 and Django 1.3 beta 1, which introduced protection from arbitrary filtering via URL parameter in the admin.