'list' object has no attribute 'model'

Question

I want to order all stories by average rating, when i type in url.../stories?ordering=average_rating it brings error: 'list' object has no attribute 'model'

    def get_queryset(self):
        queryset = Story.objects.all()
        ordering = self.request.query_params.get('ordering', None)
        if ordering == 'average_rating':
            return sorted(queryset, key=lambda s: s.average_rating)
        return queryset

class Story(models.Model):
    ...
    @property
    def average_rating(self):
        average_rating = self.ratings.all().aggregate(Avg('rating'))['rating__avg']
        if average_rating is not None:
            return round(float(average_rating), 2)

        return None

Solution

class StoryViewSet(viewsets.ModelViewSet):
    queryset = Story.objects.all()

    def filter_queryset(self, queryset):
        ordering = self.request.query_params.get('ordering')

        if ordering == 'average_rating':
            return sorted(queryset, key=lambda s: s.average_rating, reverse=True)
        return queryset

Answer 1

sorted(queryset, key=lambda s: s.average_rating) this returns a list, while get_queryset should return a queryset

You can try something like this:

def get_queryset(self):
    queryset = Story.objects.all()
    ordering = self.request.query_params.get('ordering', None)
    if ordering == 'average_rating':
        return queryset.annotate(rating_avg=Avg('ratings__rating')).order_by('rating_avg')
    return queryset

Answer 2

As the name implies, get_queryset needs to return a queryset, not a list.

Luckily your entire query and ordering can be done in the database; you don't need the average_rating method.

    queryset = Story.objects.annotate(average_rating= Avg('ratings__rating'))
    ordering = self.request.query_params.get('ordering', None)
    if ordering == 'average_rating':
        queryset = queryset.order_by("average_rating")
    return queryset