Checking another field at the same time as checking a many-to-many relationship

I have a simple-ish ownership design on one of my models. It can be owned by multip开发者_StackOverflow社区le people and current owners can add other people but they have to confirm the invite before they are treated as a real owner.

class MyOwnedThing(models.Model):
    owners = models.ManyToManyField(User, through='Ownership', related_name='othings')

    def is_owner(self, user):
        return user in self.owners

class Ownership(models.Model):
    user = models.ForeignKey(User)
    myownedthing = models.ForeignKey(MyOwnedThing)

    confirmed = models.BooleanField(default=False)

The problem is MyOwnedThing.is_owner needs to check that the owner had confirmed their invite. Is there a simple way of doing that or am I left doing a separate try/except around Ownership.objects.filter(user=u, myownedthing=mot, confirmed=True)?

I typically use association tables for this type of functionality. The following hasn't been tested but should give you a general idea of what I mean:

class Resource(models.Model):
    resource = models.TextField(max_length=255)

class ResourceUser(models.Model):
    owner = models.ForeignKey(User)
    resource = models.ForeignKey(Resource)

    def is_owner(self, user, res):
        return self.filter(self.owner=user).filter(self.resource=res)