Django access nested object field in serializer

Question

I Django-Rest have a class User that contain the field first_name, and a class Account that contain the fields username and a_class_ref that is a one-to-one' relation.

How it is possible in the serializer of B to do something like :

class AccountSerializer():
    class Meta:
        model= Account
        fields= [
          'username',
          'firstname` 
        ]

Account :

class Account(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        related_name='account',
        on_delete=models.CASCADE
    )
    def username(self):
        return self.user.username <== this is the solution that I'm trying to avoid

And User is the extended AbstractUser from Django-rest-framework, that comes with a first_name = models.CharField(_('first name'), max_length=30, blank=True)

Thank you

you will need to create a serializer in order to display the information of a_class_ref, looks for nested serializer in the documentation — Xepe
– Xepe, Commented Nov 16, 2018 at 19:18
Yes but I'd like to do it a way that at the end, the json is not in "nested format", so it's transparent to the user — Boris Le Méec
– Boris Le Méec, Commented Nov 16, 2018 at 19:23
May you add the model's code? Also if instead of using those cryptic names you used the real ones it would be easier to help you. — grouchoboy
– grouchoboy, Commented Nov 16, 2018 at 19:52

slider · Accepted Answer · 2018-11-16 20:35:48Z

7

You can declare a custom field with the source attribute:

class BSerializer(serializers.ModelSerializer):
    a_field = serializers.CharField(source='a_class_ref.a_field')

    class Meta:
        model= B
        fields= ['b_field', 'a_field']

Edit

Based on the models you posted, the following should work:

class Account(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        related_name='account',
        on_delete=models.CASCADE
    )

class AccountSerializer(serializers.ModelSerializer):
    username = serializers.CharField(source='user.username')
    firstname = serializers.CharField(source='user.first_name')

    class Meta:
        model= Account
        fields= ['username', 'firstname']

edited Nov 16, 2018 at 20:35

answered Nov 16, 2018 at 19:23

slider

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9 Comments

Boris Le Méec Over a year ago

It sounds like it is exactly what I was looking for, but I still have this exception : django.core.exceptions.ImproperlyConfigured: Field name firstname is not valid for model Account. (Account is B, and firstname is a_field)

Boris Le Méec Over a year ago

I edited my original post, in B, A is a one-to-one relation field

slider Over a year ago

@BorisLeMéec you can't directly access a_fileld. Note that I'm going via a_class_ref. What is the field name on Account that you use to reference the other model?

Boris Le Méec Over a year ago

I wrote firstname = serializers.CharField(source='user.firstname') and user is the one-to-one related field in the B class, that refers to the A class

Boris Le Méec Over a year ago

That was probably a typo mistake, I just copy paste your code and it's working now thank you !

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