How to return data in custom json format?

Question

Models

class Transaction(models.Model):
    created_at = models.DateTimeField()
    transaction_type = models.ForeignKey(
        TransactionType,
        on_delete=models.CASCADE
    )

class Transfer(models.Model):
    transaction_id = models.ForeignKey(
        Transaction,
        on_delete=models.CASCADE
    )
    debit = models.ForeignKey(
        Account,
        on_delete=models.CASCADE,
        related_name='debit'
    )

Serializers for getting json

class TransferSerializer(serializers.ModelSerializer):
    class Meta:
        model = Transfer
        fields = ('created_at', 'debit',)

class TransactionSerializer(serializers.ModelSerializer):
    transfers = TransferSerializer(many=True)
    class Meta:
        model = Transaction
        fields = ('created_at', 'transaction_type', 'transfers')

Views

class TransactionViewSet(viewsets.ModelViewSet):
    queryset = Transaction.objects.all()
    serializer_class = TransactionSerializer
    pagination_class = LimitOffsetPagination

How to return data with following json format? What is the best approach? When i try to run it i getting error "Got AttributeError when attempting to get a value for field transfers on serializer TransactionSerializer."

{
  "created_at": "2019-08-18",
  "transaction_type_id": "1",
  "transfers": {"debit": "100"},
}

Nested relationships

Daniel Roseman
– Daniel Roseman

2019-11-19 08:53:00 +00:00
Commented Nov 19, 2019 at 8:53 — Daniel Roseman
– Daniel Roseman, Commented Nov 19, 2019 at 8:53

AlexandreS · Accepted Answer · 2019-11-19 12:32:21Z

1

In your Transfer model, in the transaction ForeignKey, add related_name=transfers.
In your TransactionSerializer, add the class attribute:

transfers = TransferSerializer(many=True)

EDIT: In your TransferSerializer, modify fields for fields=('created_at','transaction_type_id', 'transfers') This will give you:

{
  "created_at": "2019-08-18",
  "transaction_type_id": "1",
  "transfers": [
    {"transfer_type": 1, "debit": "100", ...},
    ...
  ],
}

edited Nov 19, 2019 at 12:32

answered Nov 19, 2019 at 11:05

AlexandreS

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7 Comments

Dmitry Rusanov Over a year ago

I getting error Got AttributeError when attempting to get a value for field `transfers` on serializer `TransactionSerializer`.

AlexandreS Over a year ago

Try specifying the TransactionSerializer meta fields with fields=('created_at','transaction_type_id', 'transfers')

Dmitry Rusanov Over a year ago

got same error Got AttributeError when attempting to get a value for field `transfers` on serializer `TransactionSerializer

AlexandreS Over a year ago

Can you update the models and serializers in your original post?

AlexandreS Over a year ago

Please add the related_name='transfers' in the transaction foreign key that is in your transfer model

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