Django Rest Framework 3.1 breaks pagination.PaginationSerializer

Question

I just updated to Django Rest Framework 3.1 and it seems that all hell broke loose.

in my serializers.py I was having the following code:

class TaskSerializer(serializers.ModelSerializer):
    class Meta:
    model = task
    exclude = ('key', ...)

class PaginatedTaskSerializer(pagination.PaginationSerializer):
    class Meta:
        object_serializer_class = TaskSerializer

which was working just fine. Now with the release of 3.1 I can't find examples on how to do the same thing since PaginationSerializer is no longer there. I have tried to subclass PageNumberPagination and use its default paginate_queryset and get_paginated_response methods but I can no longer get their results serialized.

In other words my problem is that I can no longer do this:

class Meta:
    object_serializer_class = TaskSerializer

Any ideas?

Thanks in advance

Answer 1

I am not sure if this is the completely correct way to do it, but it works for my needs. It uses the Django Paginator and a custom serializer.

Here is my View Class that retrieves the objects for serialization

class CourseListView(AuthView):
    def get(self, request, format=None):
        """
        Returns a JSON response with a listing of course objects
        """
        courses = Course.objects.order_by('name').all()
        serializer = PaginatedCourseSerializer(courses, request, 25)
        return Response(serializer.data)

Here is the hacked together Serializer that uses my Course serializer.

from django.core.paginator import Paginator, PageNotAnInteger, EmptyPage

class PaginatedCourseSerializer():
    def __init__(self, courses, request, num):
        paginator = Paginator(courses, num)
        page = request.QUERY_PARAMS.get('page')
        try:
            courses = paginator.page(page)
        except PageNotAnInteger:
            courses = paginator.page(1)
        except EmptyPage:
            courses = paginator.page(paginator.num_pages)
        count = paginator.count
    
        previous = None if not courses.has_previous() else courses.previous_page_number()
        next = None if not courses.has_next() else courses.next_page_number()
        serializer = CourseSerializer(courses, many=True)
        self.data = {'count':count,'previous':previous,
                 'next':next,'courses':serializer.data}

This gives me a result that is similar to the behavior that the old paginator gave.

{
    "previous": 1,
    "next": 3,
    "courses": [...],
    "count": 384
}

I hope this helps. I still think there has got to be a beter way to do this wiht the new API, but it's just not documented well. If I figure anything more out, I'll edit my post.

EDIT

I think I have found a better, more elegant way to do it bey creating my own custom paginator to get behavior like I used to get with the old Paginated Serializer class.

This is a custom paginator class. I overloaded the response and next page methods to get the result I want (i.e. ?page=2 instead of the full url).

from rest_framework.response import Response
from rest_framework.utils.urls import replace_query_param

class CustomCoursePaginator(pagination.PageNumberPagination):
    def get_paginated_response(self, data):
        return Response({'count': self.page.paginator.count,
                         'next': self.get_next_link(),
                         'previous': self.get_previous_link(),
                         'courses': data})

    def get_next_link(self):
        if not self.page.has_next():
            return None
        page_number = self.page.next_page_number()
        return replace_query_param('', self.page_query_param, page_number)

    def get_previous_link(self):
        if not self.page.has_previous():
            return None
        page_number = self.page.previous_page_number()
        return replace_query_param('', self.page_query_param, page_number)

Then my course view is very similar to how you implemented it, only this time using the Custom paginator.

class CourseListView(AuthView):
    def get(self, request, format=None):
        """
        Returns a JSON response with a listing of course objects
        """
        courses = Course.objects.order_by('name').all()
        paginator = CustomCoursePaginator()
        result_page = paginator.paginate_queryset(courses, request)
        serializer = CourseSerializer(result_page, many=True)
        return paginator.get_paginated_response(serializer.data)

Now I get the result that I'm looking for.

{
    "count": 384,
    "next": "?page=3",
    "previous": "?page=1",
    "courses": []
}

I am still not certain about how this works for the Browsable API (I don't user this feature of drf). I think you can also create your own custom class for this. I hope this helps!