Django Rest Framework，具有自定义分页的Rest API

Question

I am using Django Rest Framework.
I have the following situation:

I have a table with some elements (for example 10k elements).
I also have an unique index in this model:

....
Element i-1
Element i
Element i+1
Element i+2
....

I need to have a REST API with the following response:

GET Elements by center Index: i

and I need to return a set of result that contains N elements that are before and N elements that are after the element i .

Using the pagination is possible to navigate in this set of results: Using PREV I can request the previous page and using NEXT I can request the next page... Example:

Get elements by center index = i

PREV:....

Result:
[
Element k
Element k+1
......
Element i
......
Element w
Element w+1
]
NEXT:....

Answer 1

In DRF documentation on pagination is stated that it is possible to write a custom pagination method:

To create a custom pagination serializer class you should subclass pagination.BasePagination and override the paginate_queryset(self, queryset, request, view=None) and get_paginated_response(self, data) methods:

• The paginate_queryset method is passed the initial queryset and should return an iterable object that contains only the data in the >requested page.
• The get_paginated_response method is passed the serialized page data and should return a Response instance

So we are going to do just that:

BASIC EXAMPLE

from rest_framework.pagination import BasePagination


class CenterPointPagination(BasePagination):
    default_center = 0
    default_radius = 5
    center_query_param = 'center'
    radius_query_param = 'radius'        

    def paginate_queryset(self, queryset, request, view=None):
        center = request.get(center_query_param, default_center)
        radius = request.get(radius_query_param, default_radius)

        start = center - radius if center - radius > 0 else 0
        finish = center + radius
        return list(queryset[start:finish])

    def get_paginated_resposne(self, data):
        return Response(OrderedDict([
            'center': center,
            'radius': radius,
            'results': data
        ]))

That pretty much is what you need as a base.
You will have to customize it further to suite your needs.
To get some ideas on how to do that, have a look at the source code of

• LimitOffsetPagination
• PageNumberPagination
• and everything else in pagination