On Wednesday, February 16, 2011 12:36:49 AM UTC, Margie Roginski wrote:
>
> Say I am using an intermediary model like that in the doc:
>
> class Person(models.Model):
> name = models.CharField(max_length=128)
>
> class Group(models.Model):
> name = models.CharField(max_length=128)
> members = models.ManyToManyField(Person, through='Membership')
>
> class Membership(models.Model):
> person = models.ForeignKey(Person)
> group = models.ForeignKey(Group)
> date_joined = models.DateField()
>
> For a given group, say I want to go through the persons in the group
> and print the date each joined the group.
>
> beatles = Group.objects.get(name="beatles")
> for person in group.members.all():
> # get join date for person
>
> What's the best way to do this? It seems to me that I have to add a
> related_name to the person field of Membership like this:
>
> person = models.ForeignKey(Person, related_name="memberships")
>
> and then traverse backward from the person back to the membership,
> filtering to find the correct membership based on the group name. Can
> someone tell me if there is a better way? So I'm thinking I have to
> do this:
>
> beatles = Group.objects.get(name="beatles")
> for person in group.members.all():
> joinDate = person.memberships.filter(group_name="beatles")
> [0].date_joined
>
> Thanks for any pointers,
>
> Margie
It's easier than that. You can get all memberships for a group in one go:
memberships =
Membership.objects.filter(group__name="beatles").select_related()
for m in memberships:
print m.person.name, m.date_joined
--
DR.
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