Django Rest Framework排序篩選器，按嵌套列表長度排序

Question

我在全球範圍內使用OrderingFilter通過settings.py，它的效果很好。

現在我想訂購一個來自ManyToManyField的嵌套列表的大小。這可能與默認OrderingFilter？

如果不是，有沒有一種方法可以通過自定義過濾器來實現，同時將查詢參數ordering保留在url（http://example.com/recipes/?ordering=）中。爲了一致性。

哦，ManyToManyField是一個通過表一。

這些都是我models.py：

class Recipe(models.Model): 
    name = models.CharField(max_length=255) 
    cook_time = models.FloatField() 
    ingredients = models.ManyToManyField(IngredientTag, through=Ingredient) 

我serializers.py：

class IngredientTagSerializer(serializers.ModelSerializer): 
    class Meta: 
     model = IngredientTag 
     fields = ('id', 'label') 

class IngredientSerializer(serializers.ModelSerializer): 
    class Meta: 
     model = Ingredient 
     fields = ('amount', 'unit', 'ingredient_tag') 
     depth = 1 

class RecipeSerializer(serializers.ModelSerializer): 
    ingredients = IngredientSerializer(source='ingredient_set', many=True) 

    class Meta: 
     model = Recipe 
     fields = ('id', 'url', 'name', 'ingredients', 'cook_time') 
     read_only_fields = ('owner',) 
     depth = 2 

而且我views.py：

class RecipeViewSet(viewsets.ModelViewSet): 
    """ 
    API endpoint that allows recipes to be viewed or edited. 
    """ 
    queryset = Recipe.objects.all().order_by() 
    serializer_class = RecipeSerializer 
    permission_classes = (DRYPermissions,) 
    ordering_fields = ('cook_time',) #Need ingredient count somewhere? 

謝謝！

Answer 1

嘗試：

class RecipeSerializer(serializers.ModelSerializer): 
    ingredients = IngredientSerializer(source='ingredient_set', many=True) 
    ingredients_length = serializers.SerializerMethodField() 

    class Meta: 
     model = Recipe 
     fields = ('id', 'url', 'name', 'ingredients', 'cook_time') 
     read_only_fields = ('owner',) 
     depth = 2 

    def get_ingredients_length(self, obj): 
     return obj.ingredients.count() 

然後爲了通過ingredients_length

編輯

在model.py，嘗試this：

@property 
    def ingredient_length(self): 
     return self.ingredient_set.count()