Create a Book instance with multiple tags in Django REST Framework

Using Django Getting Started
1

I am new to Django and I have created 2 models named ‘Book’ and ‘Tag’ and I tried this way-

Model Class

class Tag(models.Model):

    name = models.CharField(max_length=50, unique=True)


    def __str__(self):
        return self.name + '___'

class Book(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    title = models.CharField(max_length=100)
    tags = models.ManyToManyField(Tag)

    def __str__(self):
        return self.title

Searializer Class

class TagSerializer(serializers.ModelSerializer):

    class Meta:
        model = Tag
        fields = ['id', 'name']

class BookSerializer(serializers.ModelSerializer):
    tags = serializers.ListField(child=serializers.CharField())

    class Meta:
        model = Book
        fields = ['id', 'title', 'tags']

    def save(self, **kwargs):
        tags = self.validated_data.pop('tags', [])
        book = BookModel.objects.create(**self.validated_data)

        if len(tags):
            tag_objs = []
            for tag_name in tags:
                tag_obj, created = Tag.objects.get_or_create(name=tag_name)
                tag_objs.append(tag_obj)
                book.tags.add(tag_obj) # Having an error in this line

View Class

class BookList(APIView):
    """List all Book and create new one in Book app"""

    def get(self, request, format=None):
        book = Book.objects.all()
        serializer = BookSerializer(book, many=True)

        return Response(serializer.data, status=status.HTTP_200_OK)

    def post(self, request, format=None):
        data = request.data

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

Here, My request body will be-

{
    title: 'Essential English Grammar',
    tags: ['lesson', 'english']
}

And I need the following response with get request-

{
    id: UUID
    title: 'Essential English Grammar',
    tags: ['lesson', 'english']
}

I need reverse relationship means I will be able to fetch all Books with a Tag. Please help me to solve this problem

2

ManyToMany relationships work the same and equally well in both directions.

Review the docs and examples at Many-to-many relationships | Django documentation | Django

3

Thanks sir, I have used Many-to-many relationship. But a problem I am facing in the Serializer’s save method. I mentioned with # comment. Could you please solve this issue?

4

What is the specific error you are receiving? Please post the traceback.

5

Error:
“Got KeyError when attempting to get a value for field tags on serializer BookSerializer.\nThe serializer field might be named incorrectly and not match any attribute or key on the OrderedDict instance.\nOriginal exception text was: ‘tags’.”

Serializer class

book.tags.add(tag_obj) # Having an error in this line

Here I guess, tag_obj is being added to the book instance (id: uuid, tag: something) but I want my response model like,

{ ....
    tags: ['lesson']
}

not

tags: {
            id: uuid,
            name: 'lesson'
          }

Thanks for your kind response sir.

6

Please post the complete traceback from the error message you’re receiving.