Django - Reverse Lookup Using ManyToManyField

Question

I am trying to execute code from django docs:

class Person(models.Model):
    name = models.CharField(max_length=128)

    def __unicode__(self):
        return self.name

class Group(models.Model):
    name = models.CharField(max_length=128)
    members = models.ManyToManyField(Person, through='Membership')

    def __unicode__(self):
        return self.name

class Membership(models.Model):
    person = models.ForeignKey(Person)
    group = models.ForeignKey(Group)
    date_joined = models.DateField()
    invite_reason = models.CharField(max_length=64)


>>> ringo = Person.objects.create(name="Ringo Starr")
>>> paul = Person.objects.create(name="Paul McCartney")
>>> beatles = Group.objects.create(name="The Beatles")
>>> m1 = Membership(person=ringo, group=beatles,
...     date_joined=date(1962, 8, 16),
...     invite_reason= "Needed a new drummer.")
>>> m1.save()
>>> beatles.members.all()
[<Person: Ringo Starr>]
>>> ringo.group_set.all()

My model looks like this:

class Trip(models.Model):
    members = models.ManyToManyField(User,blank=True,null=True,through='TripReservation')

But when I call user.group_set.all () for a given user instance, I get an error that there is no group_set attribute

Answer 1

First, do you use an end-to-end model? You have it there, but you do not have it. If you do not want this, you do not need it.

I would add a related name, for example:

class Trip(models.Model):
    members = models.ManyToManyField(User,blank=True,null=True, related_name='user_trips')

Then you can call:

user.user_trips.all()

I called it "user_trips" and not "shutdowns" because if it is not a unique name, it can cause conflicts.

If you use an end-to-end model, it will look something like this:

#User is defined in django.auth

class Trip(models.Model):
    members = models.ManyToManyField(User,blank=True,null=True, related_name='user_trips', through='TripReservation')

class TripReservation(models.Model):
    user = models.ForeignKey(User)
    trip = models.ForeignKey(Trip)
    registered = models.DateField()

, TripReservation Trip, , Trip. , TripReservation.registered, .

:

user.user_trips.all()