Not Null constrained error on field handled in views.py

Question

I am working with django rest framework. I have Product and Review models. Review is related to Product like so;

class Product(models.Model):
    name = models.CharField(max_length=200, null=False, blank=False)
    description = models.TextField(max_length=2000, null=False, blank=False)
    owner = models.ForeignKey(User, on_delete=models.CASCADE)
    slug = models.SlugField(unique=True)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    is_featured = models.BooleanField(default=False)
    created= models.DateTimeField(auto_now_add=True)

class Review(models.Model):
    author = models.ForeignKey(User, on_delete=models.CASCADE)
    product= models.ForeignKey(Product, on_delete=models.CASCADE)
    title = models.CharField(max_length=80, blank=False, null=False)
    body = models.TextField(max_length=400, blank=False, null=False)
    is_approved = models.BooleanField(default=False)
    created = models.DateTimeField(auto_now_add=True)

I wrote a serializer class for the review:

class ReviewSerializer(serializers.ModelSerializer):
    author = UserSerializer(read_only=True)
    class Meta:
        model = Review
        fields = ['id', 'author', 'title', 'body', 'is_approved', 'created']

    def create(self, validated_data):
        title = validated_data.get('title')
        body = validated_data.get('body')
        author = self.context['request'].user
        review = Review.objects.create(title=title, body=body, author=author)
        return review

and in my views.py, i have this;

class ReviewCreateView(CreateAPIView):
    serializer_class = ReviewSerializer
    queryset = Review.objects.all()
    permission_classes = [IsAuthenticated,]
    authentication_classes = [TokenAuthentication,]

    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        product_id = kwargs.get('product')
        product = Product.objects.get(id=product_id)
        serializer.save(product=product)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

in my urls urlpatterns:

path('api/review/new/<product>/', ReviewCreateView.as_view(), name="create-review"),

Issue is when i send a review from the frontend to that api, i keep getting a Not Null constraint error like so: IntegrityError at /api/review/new/23/ NOT NULL constraint failed: products_review.product_id

I have handled the product saving inside the CreateAPIView in my views, but for some reasons Django isn't picking it. How do i make this work please? Any assistance will be appreciated. Please note that answers for similar questions i found here didn't work for me.

Call serializer .save() in the view will create a new instance, but you saved also in Serializer.create method using create, here you just need to return a instance ready for save — minglyu
– minglyu, Commented Jun 30, 2020 at 10:54
@minglyu thanks. You mean in serializer i'm not supposed to save? — banky
– banky, Commented Jun 30, 2020 at 11:34

c6754 · Accepted Answer · 2020-06-30 20:41:49Z

2

You are almost right. You passed the product instance, so it should be included in the validated_data for the ReviewSerializer.create method. But you don't use it when you are actually creating the review instance.

class ReviewSerializer(serializers.ModelSerializer):
    author = UserSerializer(read_only=True)
    class Meta:
        model = Review
        fields = ['id', 'author', 'title', 'body', 'is_approved', 'created']

    def create(self, validated_data):
        title = validated_data.get('title')
        body = validated_data.get('body')
        author = self.context['request'].user
        product = validated_data.get('product')
        review = Review.objects.create(
            title=title, 
            body=body, 
            author=author, 
            product=product
        )
    return review

https://www.django-rest-framework.org/api-guide/serializers/#passing-additional-attributes-to-save

Also why can't you just have a product field on your review serializer?

answered Jun 30, 2020 at 20:41

c6754

8871 gold badge9 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

banky Over a year ago

Thanks @c6754. I passed the product as a kwarg in the url, using the product ID,not as part of the request data, so I don't think it will be part of the validated data.

c6754 Over a year ago

Can you print out the value of product in the ReviewSerializer.create method before the Review.objects.create method is called?

Mad Wombat Over a year ago

I think @c6754 is right. Review.objects.create(title=title, body=body, author=author) attempts to save the review, but you don't have a product yet. Try to use Review(title=title, body=body, author=author) instead to create an unsaved instance and then save in the view once product is set.

Collectives™ on Stack Overflow

Not Null constrained error on field handled in views.py

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related