Serializer for inherited model

Question

I have following models declared:

class Parent(models.Model):
    active = models.BooleanField(default=False)

class Child(Parent)
    name = models.CharField(max_length=100, unique=True)

and serializer:

class ChildSerializer(serializers.ModelSerializer):

    class Meta:
        model = Child
        fields = ('active', 'name')

At glance everything seems to be ok, it's correctly generated in the browsable api. Neverthless when I want to update both fields only 'active' is updated.

When I do put in return I receive correct resonse:

{
  "active": true,
  "name": "foo"
}

But the name field is not updated at all. I went further and tried to implemented custom update method in the serializer:

def update(self, instance, validated_data):
    print(str(type(instance)))
    return instance

After that in a put response I'm receiving only active field ?:

{
  "active": true,
}

And on console even more astonishing:

rest_1  | <class 'applic.models.Person'>

I'm completely lost :) Why on earth serializer treats explicitly provided Child model as a Person ? How to force ChildSerializer to work on Child model ?

Thank you in advance Piotr

your models are not related what is the relationship is it 1 to 1, 1 to many ..etc ? — Ali Ezzat Odeh, Feb 15 '18 at 09:01
hi, when you derive one model from another their relationship is 1 to 1 (at least it looks like this in db), except this, there is no other relationship — Piotr, Feb 15 '18 at 09:19
Ok, the problem is with update but creation is working fine ? — Ali Ezzat Odeh, Feb 15 '18 at 10:23

score 0 · Accepted Answer · answered Feb 15 '18 at 11:12

Change your models.py as below,

class Parent(models.Model):
    active = models.BooleanField(default=False)


class Child(Parent):
    parent = models.OneToOneField(Parent)
    name = models.CharField(max_length=100, unique=True)

and try ModelViewSet in views.py as below,

class YourViewClass(ModelViewSet):
    serializer_class = ChildSerializer
    queryset = Child.objects.all()

Assuming your api end-point is /api/vi/sample/, then

to add instance, use POST method on /api/vi/sample/ payload will be as below

{
    "active": true,
    "name": "name_choice"
}

to edit instance, PUT or PATCH on /api/vi/sample/instance_id where instance_id is an integer representing the primary key of the Child instance (example :/api/vi/sample/1 ). Updated payload as below,

{
    "active": false,
    "name": "name_choice_new_change"
}

If you'd like to see the instance_id, update your serializer as follows,

class ChildSerializer(serializers.ModelSerializer):
    class Meta:
        model = Child
        fields = ('id', 'active', 'name')

Hello, thank you very much for the solution. Nevertheless I'm still super curious why is that (because above trick it's more workaround IMHO). For me it looks like a bug, but I'm not sure. Can anyone explain it to me ? — Piotr, Feb 15 '18 at 13:03
`Parent` and `Child` models are dependent and they must be in `OneToOne Relationship` as you mentioned in the question. In Django, this is how it implemented. This is the official doc for `one to one` relationship, https://docs.djangoproject.com/en/2.0/topics/db/examples/one_to_one/ — JPG, Feb 15 '18 at 16:29

Serializer for inherited model

1 Answers1