How can I get the count of nested model relationship?

Question

Here are my model relationships:

|---Retailer
    |---Product
        |---Coupon

Now I have a view that returns me each retailer with its products:

class ProductList(APIView):
    def get(self, request):
        retailer = Retailer.objects.all()
        serializer = RetailerSerializer(retailer, many=True)
        data = serializer.data
        return JsonResponse({'data': data}, safe=False)

And here's RetailerSerializer:

class RetailerSerializer(serializers.ModelSerializer):
    products = ProductSerializer(many=True, read_only=True)
    class Meta:
        model = Retailer
        fields = ['name', 'website','description', 'products']
        depth = 1

Now I want to get count coupons in each product. What should i do?

add your relevant portions of model class – JPG May 17 '20 at 06:31 — JPG, May 17 '20 at 06:31
https://stackoverflow.com/a/14581826/10349590 – robinsax May 17 '20 at 06:32 — robinsax, May 17 '20 at 06:32

score 1 · Answer 1 · answered May 17 '20 at 06:35

1

Add following line into your ProductSerializer

def to_representation(self, instance):
    reps = super().to_representation(instance)
    reps['coupons_count'] = instance.coupon_set.all().count()
    return reps

Rename coupon_set in instance.coupon_set.all().count() with your backward relation name. The default name is coupon_set but you can change it by specify related_name in Coupon model that related into Product model

answered May 17 '20 at 06:35

Eby Sofyan

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Thank a lot. it worked but I think I should edit my question title can you help me with that? – Vala Khosravi May 19 '20 at 05:54

How can I get the count of nested model relationship?

1 Answers1