I’m sending an object like this to my Django backend to update the.

{
  id: 1,
  firstName: 'Foo',
  lastName: 'Bar',
  items: [
    {
      id:1,
      cost: 150,
      ....
      calculatedValue: 0
    },
    {
      id: 2,
      cost: 100,
      ....
      calculatedValue: 0
    }
  ]
}

Here are the Models

class Parent(models.Model):
    firstName = models.models.TextField()
    lastName = models.TextField()

class Item(models.Model):
    parent = models.ForeignKey(Parent, related_name='items', on_delete=models.CASCADE)
    cost = models.FloatField(blank=True, default=0, null=True)
    calculatedValue = models.FloatField(blank=True, default=0, null=True)

Here are the serializer

class ParentSerializer(serializers.ModelSerializer):
    items = ItemSerializer(many=True, read_only=True)
    class Meta:
        model = Parent
        fields = ('id', 'firstName', 'lastName')

class ItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = Item
        fields = ('id', 'cost', 'calculatedValue')

My intention is perform the operation for the calculatedValue on the server during the post or put calls. The issue I’m running into is the value I’m computing isn’t saving to the database.

    def update(self, request, *args, **kwargs):
        # I set the values on the request.data object here
        setValues(request.data)

        partial = kwargs.pop('partial', False)
        instance = self.get_object()

        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)
        self.perform_update(serializer)

        if getattr(instance, '_prefetched_objects_cache', None):
            instance._prefetched_objects_cache = {}

        #save transaction
        items = request.data['items']
        for item in items:

            itemInstance = Item.objects.get(id=item['id'])
            itemSerializer = ItemSerializer(itemInstance, data=transaction,  partial=False)
            itemSerializer.is_valid(raise_exception=True)
            itemSerializer.save()
            
            #the correct value prints here
            print(f'instance after save {itemSerializer.data}')

        return Response(serializer.data)

Even though the itemSerializer.data shows the values have been saved, when I do a get on the parent object, the changes aren’t there.

How do I get these values to save?