Manipulate data on serializer before creating model instance in DangoRestFramework - django-rest-framework

Question

I have three related models as such
Order model
class Order(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4)
Name = models.CharField(max_length=250)
orderType = models.ForeignKey(OrderType, on_delete=models.CASCADE, null=True)
class Meta:
ordering = ['id']
def __str__(self):
return '{}'.format(self.Name)enter code here
OrderPricing Model
class OrderPricing(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4)
TotalPrice = models.DecimalField(decimal_places=2, max_digits=10)
#related field
order = models.ForeignKey(Order, on_delete=models.CASCADE, null=True)
class Meta:
ordering = ['order']
def __str__(self):
return self.TotalPrice
OrderType Model
class OrderType(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4)
Name = models.CharField(max_length = 100)
Premium = models.BooleanField()
class Meta:
ordering = ['id']
Let's ignore the order in which the models appear above.
I have three SerializerModels for each model.
I can crud each model on the BrowsableAPI
Q1:
From the browsableAPI I can create an Order.
I haven't gotten to the 'Writable Nested Serializer' yet and I believe Django has that figured out in their docs through the drf-writable-nested class.
I have two orderTypes
1 = {'Not Premium':'False'} #not Premium
2 = {'Premium':'True'} #Premium
Assume I have a variable order_price = 5 #£5
How can I
Create an order,
If order is premium, then set order_price to 10 #order_price * 2
If order is NOT premium, then set order_price to 5
Create an instance of OrderPricing, that's related to the order. Also, pass the order_price variable to the property TotalPrice when creating the instance
from what I have seen and tried, I can override the Create() on the serializer as such
class OrderSerializer(WritableNestedModelSerializer):
"""OrderSerializer"""
# orderPricing = OrderPricingSerializer(required=False)
class Meta:
model = Order
fields = ('__all__')
def create(self, validated_data):
#create instance of order
#determine of order is premium
typeid = uuid.UUID(validated_data.pop('orderType'))#get FK value
isPremium = OrderType.objects.get(id = str(typeid.id))#determine if **Premium** is True/False
# set/calculate the price of the order
#create a related instance of OrderPricing
Q2
I am aware of GenericViews and the CreateModelMixin, what I don't know is, which is better, overriding the .create() at the serializer or overriding the CreateModelMixin method at the GenericView

Answer 1

Well, where to put business logic is always question hard to answer.
You have multiple places where it can be - view, serializer, model or some other separate module/service.
All have pros and cons- you can find many articles on this topic.
But in your case, I would probably go with perform_create of your view and I would create a method in the serializer which would update the price. If I needed to use the code to update price, I'd move to separate shared module and call it from there.
So let's say you use CreateModelMixin or better ListCreateAPIView
class YourView(ListCreateAPIView):
serializer = OrderSerializer
queryset = your_queryset
def perform_create(self, serializer):
serializer.update_price()
serializer.save()
perform_create is called after data is validated, so you can access the validated data.
update_price is your code where you update the price.
You can argue to move this logic to serializer's create or save method but they do many other things, so unless you need to override these methods for other reasons - you can take advantage of the perform_create method.