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"""
Pagination serializers determine the structure of the output that should
be used for paginated responses.
"""
from __future__ import unicode_literals
from rest_framework import serializers
from rest_framework.templatetags.rest_framework import replace_query_param
class NextPageField(serializers.Field):
"""
Field that returns a link to the next page in paginated results.
"""
page_field = 'page'
def to_native(self, value):
if not value.has_next():
return None
page = value.next_page_number()
request = self.context.get('request')
url = request and request.build_absolute_uri() or ''
return replace_query_param(url, self.page_field, page)
class PreviousPageField(serializers.Field):
"""
Field that returns a link to the previous page in paginated results.
"""
page_field = 'page'
def to_native(self, value):
if not value.has_previous():
return None
page = value.previous_page_number()
request = self.context.get('request')
url = request and request.build_absolute_uri() or ''
return replace_query_param(url, self.page_field, page)
class DefaultObjectSerializer(serializers.Field):
"""
If no object serializer is specified, then this serializer will be applied
as the default.
"""
def __init__(self, source=None, context=None):
# Note: Swallow context kwarg - only required for eg. ModelSerializer.
super(DefaultObjectSerializer, self).__init__(source=source)
class PaginationSerializerOptions(serializers.SerializerOptions):
"""
An object that stores the options that may be provided to a
pagination serializer by using the inner `Meta` class.
Accessible on the instance as `serializer.opts`.
"""
def __init__(self, meta):
super(PaginationSerializerOptions, self).__init__(meta)
self.object_serializer_class = getattr(meta, 'object_serializer_class',
DefaultObjectSerializer)
class BasePaginationSerializer(serializers.Serializer):
"""
A base class for pagination serializers to inherit from,
to make implementing custom serializers more easy.
"""
_options_class = PaginationSerializerOptions
results_field = 'results'
def __init__(self, *args, **kwargs):
"""
Override init to add in the object serializer field on-the-fly.
"""
super(BasePaginationSerializer, self).__init__(*args, **kwargs)
results_field = self.results_field
object_serializer = self.opts.object_serializer_class
if 'context' in kwargs:
context_kwarg = {'context': kwargs['context']}
else:
context_kwarg = {}
self.fields[results_field] = object_serializer(source='object_list', **context_kwarg)
class PaginationSerializer(BasePaginationSerializer):
"""
A default implementation of a pagination serializer.
"""
count = serializers.Field(source='paginator.count')
next = NextPageField(source='*')
previous = PreviousPageField(source='*')
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