CODEWITHSUNDEEP
djangomodelforeign-keys
Aidan Ewen
Aidan Ewen

Reputation: 13308

django model save error 'object has no attribute "field_id"

I've got a simple django model with 2 optional fields. I'm getting an error when I try to save the model.

class Cart(models.Model):
    shipping = models.ForeignKey(ShippingRate, blank=True, null=True)
    date_created = models.DateTimeField(blank=True, null=True)

    def save(self, *args, **kwargs):
        if not self.date_created:
            self.date_created = datetime.datetime.now()
        super(Cart, self).save(*args, **kwargs)

Using a simple view to save a cart object, I get the following error - 

'Cart' object has no attribute 'shipping_id'

It's the call to super() that's failing. I've had a look at the database and I've got the fields 'id', 'date_created' and 'shipping_id' on my table.

I'm managing my db with south, and I've tried removing, migrating and replacing fields but that doesn't work. It's a strange one - I expect I'm missing something obvious but I haven't spotted it yet..

UPDATE

I've tried removing the save() override, and even swapping out fields (then migrating with south). I swapped out the shipping field for a new shipping_rate field -

class Cart(models.Model):
    shipping_rate = models.ForeignKey(ShippingRate, blank=True, null=True)
    date_created = models.DateTimeField(blank=True, null=True)

This time I get the same error on save, only it's the date_created field that's causing it.

'Cart' object has no attribute 'date_created'

As before, I've had a glance at my (postgres) database, and I can see the 3 fields I expect - id, shipping_rate_id, and date_created.

UPDATE 2

OK, I've reduced my code to -

#models
class Cart(models.Model):
    shipping_rate = models.ForeignKey(ShippingRate, blank=True, null=True)
    modified = models.DateTimeField(blank=True, null=True)

    class Meta():
        app_label = 'cart'

#views
def add_to_cart(request):
    if 'cart' in request.session:
        cart = request.session['cart']
    else:
        cart = Cart()
    if not cart.pk:
        cart.save()
    return HttpResponse('ok')

And my traceback -

Traceback:
File "/Users/aidan/Environments/bbhq/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/Users/aidan/Code/bbhq/bbhq/cart/views.py" in add_to_cart
  71.             cart.save()
File "/Users/aidan/Environments/bbhq/lib/python2.7/site-packages/django/db/models/base.py" in save
  463.         self.save_base(using=using, force_insert=force_insert, force_update=force_update)
File "/Users/aidan/Environments/bbhq/lib/python2.7/site-packages/django/db/models/base.py" in save_base
  551.                 result = manager._insert([self], fields=fields, return_id=update_pk, using=using, raw=raw)
File "/Users/aidan/Environments/bbhq/lib/python2.7/site-packages/django/db/models/manager.py" in _insert
  203.         return insert_query(self.model, objs, fields, **kwargs)
File "/Users/aidan/Environments/bbhq/lib/python2.7/site-packages/django/db/models/query.py" in insert_query
  1575.     query.insert_values(fields, objs, raw=raw)
File "/Users/aidan/Environments/bbhq/lib/python2.7/site-packages/django/db/models/sql/subqueries.py" in insert_values
  170.                 value = getattr(obj, field.attname)

Exception Type: AttributeError at /cart/add_to_cart
Exception Value: 'Cart' object has no attribute 'shipping_rate_id'

Upvotes: 0

Views: 776

Answers (1)

Daniel Roseman
Daniel Roseman

Reputation: 599490

As mentioned in the comment, there was an old entity in the session that was pickled before the new fields were added.

Upvotes: 2

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