AttributeError at /apiv2/api/processorder/order/

Question

I am trying to post multiple data into my DataBase Using Django Rest framework (DRF).

AttributeError at /apiv2/api/processorder/order/ Got AttributeError when attempting to get a value for field subcategory on serializer MyProcessOrderSerializer. The serializer field might be named incorrectly and not match any attribute or key on the list instance. Original exception text was: 'list' object has no attribute 'subcategory'.

models.py

class SubCategory(models.Model):

    category = models.ForeignKey(Category, related_name='subcategory', on_delete=models.CASCADE)
    name = models.CharField("Food Name", max_length=50, help_text="Name of The Food")    
    price = models.DecimalField("Food Price", max_digits=5, decimal_places=2)
    quantity = models.PositiveIntegerField("Qty.", help_text="Quantity of the food Item you want")
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    def __str__(self):
        return f'{self.name}'

    class Meta:
        verbose_name = 'SubCategory'
        verbose_name_plural = 'SubCategories'

class Order(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    bike = models.ForeignKey(User, related_name='bike', on_delete=models.CASCADE, blank=True, null=True)
    package = models.ForeignKey(PackageType, related_name='package', on_delete=models.CASCADE, blank=True, null=True)
    total_price = models.DecimalField(max_digits=10, decimal_places=2, default=0000.0)  
    qty = models.PositiveIntegerField(default=1)
    shipping_address = models.CharField("Delivery Address", max_length=150)
    paid = models.BooleanField(default=False)
    ordernote = models.TextField("Order Notes", null=True)
    shipped = models.BooleanField(default=False)
    complete = models.BooleanField(default=False) 
    received = models.BooleanField(default=False)
    refund_requested = models.BooleanField(default=False)
    refund_granted = models.BooleanField(default=False)
    ref_code = models.CharField(max_length=20, blank=True, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)


    class Meta:
        ordering = ('-created_at',)

    def __str__(self):
        return '{}'.format(self.id)


    def order(self):
        if not hasattr(self, '_order'):
            self._order = self.order.all()
        return self._order

    

    '''
    def get_total_cost(self):
        total_cost = sum(orders.get_cost() for orders in self.order.all())
        return total_cost

    '''


class ProcessOrder(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    order = models.ForeignKey(Order, related_name='order', on_delete=models.CASCADE)
    quantity = models.PositiveIntegerField("Qty.", default=1, help_text="Quantity of the food Item you want")
    #category = models.ForeignKey(Category, related_name='category', on_delete=models.CASCADE)
    subcategory = models.ForeignKey(SubCategory, on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return f'{self.order} -- {self.subcategory.name}'

serializers.py

class MyProcessOrderSerializer(serializers.ModelSerializer):

    #subcategory_name = serializers.RelatedField(source='subcategory.id', read_only=True)
    #subcategory_set = SubCategoryOrderSerializer(many=True)


    class Meta:
        model = ProcessOrder
        fields = ('quantity', 'subcategory', 'user')

        read_only_fields = ('user', ) 

    def create(self, validated_data):
        return ProcessOrder.objects.create(**validated_data)

view.pf

@api_view(['POST'])
@permission_classes([IsAuthenticated])
def processorder_view(request):
    orderuser = User.objects.get(id=request.user.id)    
    serializer = MyProcessOrderSerializer(data=request.data, many=True)
   
    if serializer.is_valid():
        order = Order.objects.create(user=orderuser, ref_code=create_ref_code())
        order.save()
        processorder = serializer.save(order=order, user=orderuser)
        return Response(MyProcessOrderSerializer(processorder).data, status=status.HTTP_201_CREATED)
    else:        #return Response("Process Order Created Successfully")
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

I am now trying to make a POST such as this but getting the above error.

[{ "quantity": 16, "subcategory": 1 }, { "quantity": 14, "subcategory": 3 }

]

Answer 1

You have to explicitly specify the relation in the serializer either with one of the built-in serializer:

Serializer relations

class MyProcessOrderSerializer(serializers.ModelSerializer):
    # StringRelatedField and PrimaryKeyRelatedField are some of the built in ones.
    subcategory = serializers.StringRelatedField(source='subcategory.id', read_only=True)
    user = serializer.PrimaryKeyRelatedField()

    class Meta:
        model = ProcessOrder
        fields = ('quantity', 'subcategory', 'user')

        read_only_fields = ('user', ) 

    def create(self, validated_data):
        # If you want to accect new subcategory object via the endpoint you need further action here, see the docs.
        return ProcessOrder.objects.create(**validated_data)

or by creating a custom subcategory serializer and then in serializer:

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        fields = ('id', 'email', 'password', 'first_name', 'last_name')
class SubCategorySerializer(serializers.ModelSerializer):
    class Meta:
      fields = # whatever fields youd'e like to include

class MyProcessOrderSerializer(serializers.ModelSerializer):
    # StringRelatedField is One of the built in ones.
    sybcategory = SubCategorySerializer()
    user = UserSerializer()

    class Meta:
        model = ProcessOrder
        fields = ('quantity', 'subcategory', 'user')

        read_only_fields = ('user', ) 

    def create(self, validated_data):
        # If you want to accect new subcategory object via the endpoint you need further action here, see the docs.
        return ProcessOrder.objects.create(**validated_data)

And, I noticed you have Foreign Key to User in process order and order itself,

You could delete the user field from the process order and access it via the order relation, for that you can specify the user field in the subcategory serializer and the subcategory serializer in the process order serializer as I showed above.

And if I understand the purpose of creating a process order model, the relation should be a One to One and not Foreign key, But maybe I'm not seeing the whole picture here.

Answer 2

I think the problem apear in request.data in this line :

      serializer = MyProcessOrderSerializer(data=request.data, many=True)

You should loop throught your object list and pass just the object not the whole list .

exemple :

{ "list_":[{"quantity": 7 ,"subcategory": 3}, {"quantity": 7 ,"subcategory": 3}] }

To get the first object from the request :

   request.data.get('list_')[0]

Answer 3

I was able to solve the problem with this code both in my views and serialize

views.py

@api_view(['POST'])
@permission_classes([IsAuthenticated])
def processorder_view(request):
    orderuser = User.objects.get(id=request.user.id) 
    data = request.data
    
    order = Order.objects.create(user=orderuser, ref_code=create_ref_code())
    

    
    if isinstance(data, list):
        serializer = MyProcessOrderSerializer(data=request.data, many=True)
        
    else:
        serializer = MyProcessOrderSerializer(data=request.data)
        
    if serializer.is_valid():
        processorder = serializer.save(order=order, user=request.user)
        return Response(status=status.HTTP_201_CREATED)
        #return HttpResponse("Question created", status=201)
    return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

serializers.py

class MyProcessOrderSerializer(serializers.ModelSerializer):

    #subcategory_name = serializers.RelatedField(source='subcategory.id', read_only=True)
    #subcategory_set = SubCategoryOrderSerializer(many=True)
    #subcategory = serializers.StringRelatedField(source='subcategory.id', read_only=True)



    class Meta:
        model = ProcessOrder
        fields = ('quantity', 'subcategory', 'user')

        read_only_fields = ('user', ) 

    def create(self, validated_data):
        return ProcessOrder.objects.create(**validated_data)

Then, I was able to send multiple data with this sample.

[
    {
        "subcategory": 1,
        "quantity": 12
    },
    {
        
        "subcategory": 3,
        "quantity": 12
    }
]