CODEWITHSUNDEEP
pythondjango
Joey Coder
Joey Coder

Reputation: 3519

Django: Accessing extra field in ManytoMany (through=)

I am trying to access the purchaser field in my ManytoMany field. I used through= to add some extra fields. However, it seems I am only able to access the event object, not the extra fields. Can someone explain to me why?

for selected_order in Order.objects.all():
    contact_exists = Contact.objects.filter(
        email=selected_order.email,
        event_related_fields=selected_order.event,
    )
    if contact_exists:
        contact = contact_exists.first()
        for x in contact.event_related_fields.all():
            print(x.purchaser)

models.py

class Contact(TimeStampedModel):
    consent = models.BooleanField(verbose_name=_("Consent"))
    email = models.EmailField(verbose_name=_("Your email"))
    first_name = models.CharField(
        max_length=100,  # TODO Length must be same as for billing model
        verbose_name=_("First name"),
        null=True,
        blank=True,
    )
    last_name = models.CharField(
        max_length=100,  # TODO Length must be same as for billing model
        verbose_name=_("Last name"),
        null=True,
        blank=True,
    )
    events = models.ManyToManyField(Event, related_name='contacts')
    event_related_fields = models.ManyToManyField(
        Event, related_name='event_related_fields', through='EventRelatedFields'
    )
    organizer = models.ForeignKey(
        Organizer, on_delete=models.PROTECT, related_name='contacts'
    )  # PROTECT = don't allow to delete the organizer if contact exists

    class Meta:
        verbose_name = _("Contact")
        verbose_name_plural = _("Contacts")
        ordering = ('created',)
        unique_together = ('email', 'organizer')

    def __repr__(self):
        return "{}: {}".format(self.__class__.__name__, self)

    def __str__(self):
        return self.email


class EventRelatedFields(TimeStampedModel):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    contact = models.ForeignKey(Contact, on_delete=models.CASCADE)
    lead = models.BooleanField(
        verbose_name='Lead', default=False
    )  # Contact who 'Signed Up'
    attendee = models.BooleanField(
        verbose_name='Attendee', default=False
    )  # Contact assigned to ticket
    purchaser = models.BooleanField(
        verbose_name='Purchaser', default=False
    )  # Contact made the order

    class Meta:
        unique_together = [['event', 'contact']]

Upvotes: 2

Views: 1475

Answers (1)

Daniel Roseman
Daniel Roseman

Reputation: 599778

You are defining two many-to-many relationships for some reason, and you've called one of them event_related_fields, with the same related name. As a result you are confusing that with the through table. But since the through table is actually calledEventRelatedFields, you would access its related objects as eventrelatedfields_set.

You should only have one m2m, events:

events = models.ManyToManyField(Event, through='EventRelatedFields', related_name='contacts')

and your class EventRelatedFields should itself set related names:

event = models.ForeignKey(Event, related_name='event_related_fields', on_delete=models.CASCADE)
contact = models.ForeignKey(Contact, related_name='event_related_fields, on_delete=models.CASCADE)

Now you can do:

for x in contact.event_related_fields.all():
    print(x.purchaser)

Upvotes: 2

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