Django rest framework cannot deal with multiple objects in model viewset

Question

I have a very simple model and its related serializer and views:

class Page(models.Model):
    user = models.ForeignKey(User)
    title = models.CharField(max_length=255)
    pub_date = models.DateTimeField(default=timezone.now)

class PageSerializer(serializers.ModelSerializer):
    class Meta:
        model = Page
        fields = ('user', 'title', 'pub_date')

class PageViewSet(viewsets.ModelViewSet):
    queryset = Page.objects.all()
    serializer_class = PageSerializer

Now I can post like this:

{
    "user": 1,
    "title": "Lorem ipsum"
}

This works fine. But I would like to post multiple objects like this:

[
    {
        "user": 1,
        "title": "Lorem ipsum one"
    },
    {
        "user": 1,
        "title": "Lorem ipsum two"
    }
]

But this gives me an error:

"non_field_errors": [

"Invalid data. Expected a dictionary, but got list."

]

So to accept multiple objects I modified the view as per the doc:

class PageViewSet(viewsets.ModelViewSet):
    queryset = Page.objects.all()
    serializer_class = PageSerializer(queryset, many=True)

But I am getting an error:

TypeError at /api/blog/pages/

'ListSerializer' object is not callable

What am I missing here?

Answer 1

You had it set up correctly before, the serializer_class should point to the class like this:

serializer_class = PageSerializer

You were right on the error, it doesn't like receiving multiple objects in the POST. One way to fix it would be to override the get_serializer method n the view, adding in many=True there.

Something like:

def get_serializer(self, *args, **kwargs):
    if "data" in kwargs:
        data = kwargs["data"]

        # check if many is required
        if isinstance(data, list):
            kwargs["many"] = True

    return super(PageViewSet, self).get_serializer(*args, **kwargs)

To answer your question in the comments: isinstance() is a Python method to check the type of an object. In this case, it's a list when passing in multiple objects, so we just check what type data is and set many=true if it's a list.

DRF docs regarding get_serializer (under methods)

Python docs regarding isinstance