How to order django rest framework queryset from serializer field? -

how can order django queryset serializer field? since field complicated, couldn't order queryset using annotate , cannot store value in model well.

edit:

serializer

class drinklistmodelserializer(serializers.modelserializer):     count_need = serializers.serializermethodfield()     url = drink_detail_url      class meta:         model = drink         fields = [             'name',             'count_need',             'thumbnail',             'url'         ]      def get_count_need(self, obj):         drink_ingredient_qs = obj.ingredients.all()         user = self.context['request'].user         user_qs = user.objects.filter(username=user.username)         if user_qs.exists() , user_qs.count() == 1:             user_obj = user_qs.first()             user_ingredient_qs = user_obj.ingredient_set.all()             return (user_ingredient_qs & drink_ingredient_qs).count()         return 0 

models:

class drink(models.model):     name                = models.charfield(max_length = 1000, null=true, blank=true)     ingredients         = models.manytomanyfield(ingredient, blank=true)     user                = models.manytomanyfield(settings.auth_user_model, blank=true)  class ingredient(models.model):     name                = models.charfield(max_length = 1000)     ingredient_category = models.foreignkey(category, null=true, blank=true)     slug                = models.slugfield(max_length=255, unique=true)     user                = models.manytomanyfield(settings.auth_user_model, blank=true) 

view

class drinklistapiview(listapiview): serializer_class = drinklistmodelserializer pagination_class = largeresultssetpagination permission_classes = [allowany]  def get_queryset(self, *args, **kwargs):     user = self.request.user     qs = drink.objects.all()     userquery = self.request.get.get('user')     query = self.request.get.get("q")     filters = self.request.get.getlist('filter')     if query:         qs = qs.filter(name__icontains=query)     elif filters:         qs = qs.filter(playlist__name__iexact=filters[0])         filter in filters[1:]:             qs = qs | drink.objects.filter(playlist__name__iexact=filter)     elif userquery , user.is_authenticated():         qs = qs.filter(user=user)     return qs.order_by('-timestamp') 

currently, i'm ordering queryset timestamp since in model self, need order 'count_need' part of serializer. tried qs = qs.annotate(count_need=count('ingredients' & user_ingredient_qs)).order_by(count_need) doesnt work since 'ingredients' string here , not drink's ingredient queryset.

one way might work implement , customize to_representation on list serializer:

def to_representation(self, data):     iterable = data.all() if isinstance(data, models.manager) else data      iterable = sorted(iterable, key=lambda x: x.count_need)      return [         self.child.to_representation(item) item in iterable     ]