DRF: How to validate a nested serializer's fields? - django

Question

I have models as below:
model: Business
name
model: Employee
business=FK(Business),
user = FK(User)
model: Item
title
units
model: PurchaseInvoice
business=FK(Business)
employee = FK(Employee)
invoice_no
date
model: PurchasedItems
parent_invoice=FK(PurchaseInvoice, related_name="purchased_items")
item = FK(Item)
quantity
rate
and serializers.py:
class PurchasedItemPOSTSerializer(serializers.ModelSerializer):
class Meta:
model = PurchasedItem
fields = ('item', 'quantity', 'rate')
def validate_quantity(self, value):
if value==0 or value is None:
raise serializers.ValidationError("Invalid quantity")
return value
def validate_rate(self, value):
if value==0 or value is None:
raise serializers.ValidationError("rate?? Did you get it for free?")
return value
class PurchaseInvoicePOSTSerializer(serializers.ModelSerializer):
purchased_items = PurchasedItemPOSTSerializer(many=True)
class Meta:
model = PurchaseInvoice
fields = ('invoice_no','date','purchased_items')
def validate_purchased_items(self, value):
if len(value)==0:
raise serializers.ValidationError("atleast one item is required.")
return value
#transaction.atomic
def create(self, validated_data):
purchased_items_data = validated_data.pop('purchased_items')
purchase_invoice = self.Meta.model.objects.create(**validated_data)
for purchased_item in purchased_items_data:
PurchasedItem.objects.create(purchase_invoice=purchase_invoice, **purchased_item)
return invoice
and views.py
class PurchaseInvoiceViewSet(viewsets.ModelViewSet):
serializer_class = PurchaseInvoicePOSTSerializer
def get_serializer_context(self):
return {'user': self.request.user, 'business_id': self.kwargs['business_id']}
def get_queryset(self, **kwargs):
return PurchaseInvoice.objects.filter(business__id=self.kwargs['business_id'])
def perform_create(self, serializer):
business = Business.objects.get(pk=self.kwargs['business_id'])
employee = get_object_or_404(Employee, business=business, user=self.request.user)
serializer.save(business=business, employee=employee)
The data sent through POST is:
{
"invoice_no": "123",
"date": "2018-07-13",
"purchased_items": [
{"item":1, "quantity":0, "rate":0}],
}
As you can see from the data above no error is raised by validate_quantity when quantity=0 and neither by validate_rate when rate=0 for the item in purchased_items.

Answer 1

You can add custom validate in your serializer. For example:
from rest_framework import serializers
class PurchasedItemPOSTSerializer(serializers.ModelSerializer):
class Meta:
model = PurchasedItem
fields = ('item', 'quantity', 'rate')
def validate(self, data):
# custom anything validate
quantity = data.get('quantity')
# recheck validate in this
if not quantity:
raise serializers.ValidationError('not valid')
return data