Django - get serialized fields from related model - django

Question

I can't figure out how to serialize a query that includes fields from a reverse related model. My models look like this. Every vote is linked to a single album:
# models.py
class Album(models.Model):
name = models.CharField(max_length=50)
class Vote(models.Model):
album = models.ForeignKey(Album, on_delete=models.CASCADE)
user_vote = models.BooleanField(default=0)
What I'd like to do is perform a query that returns all Album objects, as well as a sum of the votes attributed to that album. That's easy enough, but when I serialize the query, the "total_votes" field is lost:
# views.py
# this works fine
query = Album.objects.annotate(total_votes = Sum(vote__user_vote))
# after serialization, I lose the field "total_votes"
serialized = serializers.serialize('json', list(query))
return serialized
Unfortunately, the field "total_votes" doesn't appear in the serialized result since, according to Django documentation, "only the fields that are locally defined on the model will be serialized."
So my question is, how do I get the following serialized result (assuming there are 100 votes for Abbey Road and 150 for Astral Weeks)? Any help would be greatly appreciated.
[
{
"pk": 1,
"model": "app.album",
"fields": {
"name": "Abbey Road",
"total_votes": 100
},
{
"pk": 2,
"model": "app.album",
"fields": {
"name": "Astral Weeks",
"total_votes": 150
},
...
]

Answer 1

According to the source, there’s no way to do this using serializers.serialize. The base django serializer will only serialize local_fields on the model instance:
for field in concrete_model._meta.local_fields:
if field.serialize:
if field.remote_field is None:
if self.selected_fields is None or field.attname in self.selected_fields:
self.handle_field(obj, field)
else:
if self.selected_fields is None or field.attname[:-3] in self.selected_fields:
self.handle_fk_field(obj, field)
for field in concrete_model._meta.many_to_many:
if field.serialize:
if self.selected_fields is None or field.attname in self.selected_fields:
self.handle_m2m_field(obj, field)
In order to get what you want, you’d have to roll your own serialization function (e.g., something that converts your model to a dict and then uses the DjangoJSONEncoder).