Django 3.2.3 I'm trying to serialize object with its fields and properties methods

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I'm new to django framework, I simply want to return a model object with its attributes and properties back to an ajax call as a Json response. I have an Item model with a property balance which returns an integer value. Here is my code:

models.py

class Item(models.Model):
   entered_by = models.ForeignKey(User, on_delete=models.PROTECT)
   name = models.CharField(max_length=50, blank=True)

   @property
   def balance(self):
      return Stock.objects.filter(item_id=self.id).aggregate(Sum('quantity')).get('quantity__sum')

class Stock(models.Model):
   item = models.ForeignKey(Item, on_delete=models.PROTECT)
   name = models.CharField(max_length=50, blank=True)
   quantity = models.PositiveIntegerField()

serializers.py

from rest_framework import serializers
from .models import Item

class ItemSerializer(serializers.ModelSerializer):
   balance = serializers.SerializerMethodField(source="get_balance")

   class Meta:
      model = Item
      fields = ('entered_by', 'name', 'balance')

views.py

from stocks.serializers import *
from django.http import HttpResponse, JsonResponse

def viewItem(request):
   if request.is_ajax and request.method == "GET":
      id = request.GET.get("item_id", None)
      item = Item.objects.get(id=id)
      if item:
         serializer = ItemSerializer()
         # return serializer.data
         return JsonResponse(serializer.data, status = 200)

The output I'm seeking is a Json output like this:

{
 name:"item name",
 entered_by: null,
 balance: 10,
}

Right now this is what I'm getting

{
entered_by: null
name: ""
}

any thought will appreciated.

django-serializer django-rest-framework django-models django python
1 Answers

You have to pass the object in the serializer, so:

serializer = ItemSerializer(item)
return JsonResponse(serializer.data, status=200)

or shorthand:

return JsonResponse(ItemSerializer(item).data, status=200)

EDIT:

For the issue in your serializer, its because of source. Try to change it to:

class ItemSerializer(serializers.ModelSerializer):
   balance = serializers.SerializerMethodField()

   class Meta:
      model = Item
      fields = ('entered_by', 'name', 'balance')

   def get_balance(self, obj)
      return obj.balance
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