IntegrityError: null value in column "invoiceOwner_id" violates not-null constraint - django

Question

In my django app, i'm having difficulties whenever i want to add a new object that uses the table paymentInvoice.
The error i'm getting from my api looks like this
IntegrityError at /api/clients/invoice/
null value in column "invoiceOwner_id" violates not-null constraint
DETAIL: Failing row contains (10, INV-0006, Lix, 2020-08-04, 1, Pending, 3000, null).
NB: I haven't created the field invoiceOwner_id, postgres automatically added it or rather is using it as a representation for my invoiceOwner field
class Purchaser(models.Model):
name = models.CharField(max_length=50)
phone = models.CharField(max_length=20, unique=True)
email = models.EmailField(max_length=255, unique=True, blank=True)
image = models.ImageField(default='default.png', upload_to='customer_photos/%Y/%m/%d/')
data_added = models.DateField(default=datetime.date.today)
def __str__(self):
return self.name
class paymentInvoice(models.Model):
invoiceNo = models.CharField(max_length=50, unique=True, default=increment_invoice_number)
invoiceOwner = models.ForeignKey(Purchaser, on_delete=models.CASCADE, related_name="invoice_detail")
product = models.CharField(max_length=50, blank=True)
date = models.DateField(default=datetime.date.today)
quantity = models.PositiveSmallIntegerField(blank=True, default=1)
payment_made = models.IntegerField(default=0)
def __str__(self):
return self.invoiceOwner.name
serilizers file
class paymentInvoiceSerializer(serializers.ModelSerializer):
invoiceOwner = serializers.SerializerMethodField()
class Meta:
model = paymentInvoice
fields = '__all__'
def get_invoiceOwner(self, instance):
return instance.invoiceOwner.name
views file
class paymentInvoiceListCreateView(ListCreateAPIView):
serializer_class = paymentInvoiceSerializer
queryset = paymentInvoice.objects.all().order_by('-date')
GET result from api call.
{
"id": 1,
"invoiceOwner": "Martin",
"invoiceNo": "INV-0001",
"product": "",
"date": "2020-08-04",
"quantity": 1,
"payment_made": 0
}
Tried passing below as POST but got the main error
{
"invoiceOwner": "Becky",
"product": "Lix",
"quantity": 1,
"payment_made": 3000
}

Answer 1

"invoiceOwner" in your serializers.py is a SerializerMethodField which is readonly
that's why you get an error, you have to define the create method yourself

Answer 2

As I said in comment: You need to explicitly override the create method in your serializer since your model has foreign key invoiceOwner, just to create that instance first as a Purchaser instance.
You can try the code below:
class paymentInvoiceSerializer(serializers.ModelSerializer):
invoiceOwner = serializers.SerializerMethodField()
class Meta:
model = paymentInvoice
fields = '__all__'
def get_invoiceOwner(self, instance):
return instance.invoiceOwner.name
def create(self, validated_data):
purchaser_name = validated_data.get("invoiceOwner")
purchaser = Purchaser(name=purchaser_name,
# you need to have phone, email, since these fields are unique,
# they can't remain null
)
purchaser.save()
return paymentInvoice.objects.create(invoiceOwner = purchaser, **validated_data)