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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_representation(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_representation(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.Serializer):
"""
If no object serializer is specified, then this serializer will be applied
as the default.
"""
def to_representation(self, value):
return value
class BasePaginationSerializer(serializers.Serializer):
"""
A base class for pagination serializers to inherit from,
to make implementing custom serializers more easy.
"""
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
try:
object_serializer = self.Meta.object_serializer_class
except AttributeError:
object_serializer = DefaultObjectSerializer
try:
list_serializer_class = object_serializer.Meta.list_serializer_class
except AttributeError:
list_serializer_class = serializers.ListSerializer
self.fields[results_field] = list_serializer_class(
child=object_serializer(*args, **kwargs),
source='object_list'
)
class PaginationSerializer(BasePaginationSerializer):
"""
A default implementation of a pagination serializer.
"""
count = serializers.ReadOnlyField(source='paginator.count')
next = NextPageField(source='*')
previous = PreviousPageField(source='*')
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