how to add model field to object after serialization

Question

I have a CartItem object that I am passing from Angular to Django. I am using DRF to serialize the object. My issue is the CartItem has a Foreignkey relationship to a Cart. If a cart does not exist I am creating the cart at that time. But then I want to add that Cart to the CartItem before I save it, I think I am close but cant figure it out..

views.py

@csrf_exempt
@api_view(['POST'])
def addtocart(request):
    serializer = CartItemSerializer(data=request.data)
    customer_id = request.user.id
    cart_qs = Cart.objects.filter(customer_id=customer_id, placed=False)
    if serializer.is_valid():
        if cart_qs.exists():
            existing_cart = cart_qs[0]
            new_cartitem = CartItems.objects.create(serializer, cart = existing_cart)
            new_cartitem.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        else:
            new_cart = Cart.objects.create(subtotal=0, placed=False, order_total=0, customer=request.user)
            new_cart.save()
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
    else:
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

model.py

class Cart(models.Model):
    placed = models.BooleanField(default=False)
    customer = models.ForeignKey(CustomUser, related_name='customuser', on_delete=models.CASCADE)


class CartItems(models.Model):
    cart = models.ForeignKey(Cart, on_delete=models.CASCADE)

It is this line i need help on: new_cartitem = CartItems.objects.create(serializer, cart = existing_cart)

Also as a side thing, is this line serializer = CartItemSerializer(data=request.data) creating a CartItem object named serializer??

EDIT: You can also create the relationship from the parent model (Cart in my case) by using the _set attribute

class CartItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = CartItems
        fields = ('recipe','restaurant', 'quantity', 'delivery_date')

data = {dict: 5} {'restaurant': '3', 'recipe': 70, 'quantity': 3, 'customer': 39, 'delivery_date': '2020-05-01'}
 'restaurant' = {str} '3'
 'recipe' = {int} 70
 'quantity' = {int} 3
 'customer' = {int} 39
 'delivery_date' = {str} '2020-05-01'
 __len__ = {int} 5

if serializer.is_valid():
    if cart_qs.exists():
        existing_cart = cart_qs[0]
        new_cart_item = serializer.save()
        existing_cart.cartitems_set.add(new_cart_item)
        return Response(serializer.data, status=status.HTTP_201_CREATED)
    else:
        new_cart = Cart.objects.create(subtotal=0, placed=False, order_total=0, customer=request.user)
        new_cart.save()
        serializer(cart_id = new_cart.id)
        serializer.save()
        return Response(serializer.data, status=status.HTTP_201_CREATED)
else:
    return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

ok added to the edit, not sure how to show request.data other than what i posted hope it helps — ratrace123
– ratrace123, Commented May 16, 2020 at 3:02

Adharsh M · Accepted Answer · 2020-05-16 04:03:00Z

You can Add cart to serializer like this.

class CartItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = CartItems
        fields = ('recipe','restaurant', 'quantity', 'delivery_date','cart')

Then Modify your function like this.

def addtocart(request):
    customer_id = request.user.id
    cart = Cart.objects.filter(customer_id=customer_id, placed=False).first()
    if not cart:
        cart = Cart.objects.create(customer_id=customer_id, placed=False)

    data = request.data
    data['cart'] = cart
    serializer = CartItemSerializer(data=data)
    if serializer.is_valid():
        serializer.save()
        return Response(serializer.cleaned_data, status=status.HTTP_201_CREATED)

    else:
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Now your questions,

serializer = CartItemSerializer(data=request.data)

Returns a CartItemSerializer instance.

model_instance = serializer.save()

This would return CartItems model instance.

giveJob · Accepted Answer · 2020-05-16 04:13:34Z

0

try this

@csrf_exempt
@api_view(['POST'])
def add_to_cart(request):
    customer_id = request.user.id
    cart_qs = Cart.objects.filter(customer_id=customer_id, placed=False)
    serializer = CartItemSerializer(data=request.data)
    if cart_qs.exists():
        cart = Cart.objects.get(customer_id=customer_id, placed=False)
    else:
        cart = Cart.objects.create(subtotal=0, placed=False, order_total=0, customer=request.user)

    if serializer.is_valid():
        serializer.save(cart=cart)
        return Response(serializer.data, status=status.HTTP_201_CREATED)
    else:
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

answered May 16, 2020 at 4:13

giveJob

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1 Comment

ratrace123 Over a year ago

this worked great, before i saw this i came up with another method of doing this using the _set method from django, i show this in EDIT2

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