Displaying ForeignKey data in Django admin change/add page

I'm trying to get an attribute of a model to show up in the Django admin change/add page of another model. Here are my models:

class Download(model.Model):
    task = models.ForeignKey('Task')

class Task(model.Model):
    added_at = models.DateTimeField(...)

Can't switch the foreignkey around, so I can't use Inlines, and of course fields = ('task__added_at',) doesn't work here either.

What's the standard approach to something like this? (or am I stretching the Admin too far?)

I'm already using a custom template, so开发者_StackOverflow社区 if that's the answer that can be done. However, I'd prefer to do this at the admin level.

If you don't need to edit it, you can display it as a readonly field:

class DownloadAdmin(admin.ModelAdmin):
    readonly_fields = ('task_added_at',)

    def task_added_at(self, obj):
        return obj.task.added_at