如何订购 Django SerializerMethodField with ManytoManyField Count

Question

I want to make blog web, I want to order on a computed SerializerMethodField, such as likes_count. Here are my Code

models.py

class Post(models.Model):
   title =  models.CharField(max_length=255, unique=True)
   content = models.TextField()
   like = models.models.ManyToManyField(
        settings.AUTH_USER_MODEL, related_name='likes', blank=True)

serializer.py

class PostSerializer(serializers.ModelSerializer):
   likes_count = serializer.SerializerMethodField()
   

   class Meta:
      model = Post
      fields =[ 'title, content, likes' ]

  def get_likes_count(self, obj):
        return obj.like.count()
        

views

class PostGenericAPIView(generics.GenericAPIView):
   queryset = Post.objects.all()
   serializer_class = PostSerializer
   filter_backends = (filters.OrderingFilter)

Answer 1

You can just annotate the value of count and order by it. For example:

from django.db.models import Count


class PostGenericAPIView(generics.GenericAPIView):
   queryset = Post.objects.annotate(likes_count=Count('like')).order_by('likes_count')
   serializer_class = PostSerializer
   filter_backends = (filters.OrderingFilter)

Also, to reduce DB hits, you can directly access the value of likes_count in serializer:

class PostSerializer(serializers.ModelSerializer):
   likes_count = serializers.IntegerField()  # No need for serializer method field