Question

I’m getting this error:

The object '' has an empty attribute 'posts' and doesn't allow a default or null value.

I’m trying to get the number of ‘votes’ on a post and return it in my models.py:

class UserPost(models.Model):
    user = models.OneToOneField(User, related_name='posts')
    date_created = models.DateTimeField(auto_now_add=True, blank=False)
    text = models.CharField(max_length=255, blank=True)

    def get_votes(self):
        return Vote.objects.filter(object_id = self.id)

Here’s my resource:

class ViewPostResource(ModelResource):
    user = fields.ForeignKey(UserResource,'user',full=True)
    votes=  fields.CharField(attribute='posts__get_votes')
    class Meta:
        queryset = UserPost.objects.all()
        resource_name = 'posts'

        authorization = Authorization()
        filtering = {
            'id' : ALL,
            }

What am I doing wrong?

Answer 1

The attribute value that you have defined isn’t proper.
You can achieve what you want in a few ways.

Define a dehydrate method:

def dehydrate(self, bundle):
    bundle.data['custom_field'] = bundle.obj.get_votes()
    return bundle

Or set the get_votes as property and define the field in resource like so (I recommend this one as it is the most clear):

votes = fields.CharField(attribute='get_votes', readonly=True, null=True)

Or define it this way:

votes = fields.CharField(readonly=True, null=True)

And in the resources define the dehydrate_votes method like so:

def dehydrate_votes(self, bundle):
    return bundle.obj.get_votes()