object has no attribute 'has_next' in pagination.PaginationSerializer

[Thomas Alisi]

hey

I have a problem that feels really n00b, but didn't manage to figure out what's happening here:

class SimpleStorylineSerializer(serializers.ModelSerializer):
    class Meta:
        model = Storyline
        fields = ('text', 'language', 'featured', 'gallery', 'render_url')


class PaginatedStorylineSerializer(pagination.PaginationSerializer):
    class Meta:
        object_serializer_class = SimpleStorylineSerializer


class StorylineGallery(generics.ListAPIView):
    queryset = Storyline.objects.filter(gallery=True)
    serializer_class = PaginatedStorylineSerializer

throws an AttributeError: 'Storyline' object has no attribute 'has_next' in rest_framework/pagination.py in to_representation, line 17

using django 1.7.x and restframework 3.0.5

any idea? help greatly appreciated

[Tom Christie]

Worth checking: any chance you've install master, rather than 3.0.5?

[Thomas Alisi]

hey tom,

thanks for getting back so quickly!

I've just installed via: pip install git+ssh://g...@github.com:tomchristie/django-rest-framework.git@master

and unfortunately the problem is still there

if it's of any help, if I delete all instances from my model and call the endpoint, I get an empty list (i.e. a json array rather than an object)

[Tom Christie]

No I was meaning make sure you're on 3.0.5, not on master.

Probably not related, just wanted to check, since there's a bunch of changes to pagination in the upcoming release (which will be 3.1.0 and is now merged into master)

[Kevin Brown]

I believe the issue here is that you are setting a pagination serializer where DRF is expecting a standard serializer. As pagination serializers expect a `Page` object, they don't work well in the `serializer_class` on views.

I would try setting your `pagination_serializer_class` instead of `serializer_class`. This may require you to enable pagination if you have not done it already.

Kevin Brown

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[Thomas Alisi]

yes, I'm normally on 3.0.5. also tried with 3.0.4 and had the same issue, sorry :(

[Thomas Alisi]

ok, I think I fixed it, thanks @kevin

trouble is I find the fix quite confusing, here my findings:

1. if I just set `pagination_serializer_class` as suggested by kevin 

class StorylineGallery(generics.ListAPIView):
    queryset = Storyline.objects.filter(gallery=True)

    pagination_serializer_class = PaginatedStorylineSerializer

it throws an assertion error (generics.py in get_serializer_class, line 189) 'StorylineGallery' should either include a `serializer_class` attribute, or override the `get_serializer_class()` method.

2. if I add a serializer_class, I then have a list of results that are not actually paginated

class StorylineGallery(generics.ListAPIView):
    queryset = Storyline.objects.filter(gallery=True)

    serializer_class = StorylineSerializer
    pagination_serializer_class = PaginatedStorylineSerializer

3. if I then `enable` pagination, by adding an explicit parameter in my config, it starts working as expected

REST_FRAMEWORK = {
    'PAGINATE_BY': 20,
}

so I guess it would be probably useful to add a bit of documentation in the pagination section of DRF and be more explicit about the requirements?

thanks a lot to both

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[Tom Christie]

> so I guess it would be probably useful to add a bit of documentation in the pagination section of DRF and be more explicit about the requirements?

The pagination API kinda sucks, and is being refreshed in the upcoming 3.1.