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Django paging (II)
2022-01-31 19:04:37 【Waiting for】
This is my participation 11 The fourth of the yuegengwen challenge 15 God , Check out the activity details :2021 One last more challenge
One 、 Source analysis
For the above example , You can have questions , Why can the configuration of some class properties have different effects ? Of course, the source code has these customized configurations , Here we use PageNumberPagination Page by page , Here is PageNumberPagination Source code , It may be a little longer , Let's interpret the configuration part , The logic related to paging in other parts is not introduced here , For the interpretation part, please see the notes :
class PageNumberPagination(BasePagination):
""" A simple page number based style that supports page numbers as query parameters. For example: http://api.example.org/accounts/?page=4 http://api.example.org/accounts/?page=4&page_size=100 """# The default page size.# Defaults to `None`, meaning pagination is disabled.
page_size = api_settings.PAGE_SIZE # The number of displays per page is configured , Can be in setting Middle configuration , It can also be in a class , The current class > overall situation (settings)
django_paginator_class = DjangoPaginator # Essential use django Built in paging component
# Client can control the page using this query parameter.
page_query_param = 'page' # url Page numbers in key To configure
page_query_description = _('A page number within the paginated result set.') # describe
# Client can control the page size using this query parameter.# Default is 'None'. Set to eg 'page_size' to enable usage.
page_size_query_param = None # url The number of displays per page in the key To configure
page_size_query_description = _('Number of results to return per page.')
# Set to an integer to limit the maximum page size the client may request.# Only relevant if 'page_size_query_param' has also been set.
max_page_size = None # The maximum number of display configurations
last_page_strings = ('last',)
template = 'rest_framework/pagination/numbers.html' # Rendered template
invalid_page_message = _('Invalid page.') # Illegal information returned by the page , Of course, we can also customize
def paginate_queryset(self, queryset, request, view=None): # Get paging data
""" Paginate a queryset if required, either returning a page object, or `None` if pagination is not configured for this view. """
page_size = self.get_page_size(request) # call get_page_size Get the number of displays per page currently requested
if not page_size:
return None
paginator = self.django_paginator_class(queryset, page_size)
page_number = request.query_params.get(self.page_query_param, 1)
if page_number in self.last_page_strings:
page_number = paginator.num_pages
try:
self.page = paginator.page(page_number)
except InvalidPage as exc:
msg = self.invalid_page_message.format(
page_number=page_number, message=six.text_type(exc)
)
raise NotFound(msg)
if paginator.num_pages > 1 and self.template is not None:
# The browsable API should display pagination controls.
self.display_page_controls = True
self.request = request
return list(self.page)
def get_paginated_response(self, data):
return Response(OrderedDict([
('count', self.page.paginator.count),
('next', self.get_next_link()),
('previous', self.get_previous_link()),
('results', data)
]))
def get_page_size(self, request):
if self.page_size_query_param:
try:
return _positive_int(
request.query_params[self.page_size_query_param],
strict=True,
cutoff=self.max_page_size
)
except (KeyError, ValueError):
passreturn self.page_size
def get_next_link(self):
if not self.page.has_next():
return None
url = self.request.build_absolute_uri()
page_number = self.page.next_page_number()
return replace_query_param(url, self.page_query_param, page_number)
def get_previous_link(self):
if not self.page.has_previous():
return None
url = self.request.build_absolute_uri()
page_number = self.page.previous_page_number()
if page_number == 1:
return remove_query_param(url, self.page_query_param)
return replace_query_param(url, self.page_query_param, page_number)
def get_html_context(self):
base_url = self.request.build_absolute_uri()
def page_number_to_url(page_number):
if page_number == 1:
return remove_query_param(base_url, self.page_query_param)
else:
return replace_query_param(base_url, self.page_query_param, page_number)
current = self.page.number
final = self.page.paginator.num_pages
page_numbers = _get_displayed_page_numbers(current, final)
page_links = _get_page_links(page_numbers, current, page_number_to_url)
return {
'previous_url': self.get_previous_link(),
'next_url': self.get_next_link(),
'page_links': page_links
}
def to_html(self):
template = loader.get_template(self.template)
context = self.get_html_context()
return template.render(context)
def get_schema_fields(self, view):
assert coreapi is not None, 'coreapi must be installed to use `get_schema_fields()`'assert coreschema is not None, 'coreschema must be installed to use `get_schema_fields()`'
fields = [
coreapi.Field(
name=self.page_query_param,
required=False,
location='query',
schema=coreschema.Integer(
title='Page',
description=force_text(self.page_query_description)
)
)
]
if self.page_size_query_param is not None:
fields.append(
coreapi.Field(
name=self.page_size_query_param,
required=False,
location='query',
schema=coreschema.Integer(
title='Page size',
description=force_text(self.page_size_query_description)
)
)
)
return fields
Copy code
Two 、 Use summary
Although for paging ,django rest framework Provides us with a variety of pagination , But the most commonly used is the first PageNumberPagination, Recommended .
And the second LimitOffsetPagination, The usage scenario is when there is a large amount of data , Only care about some of the data , Recommended .
CursorPagination Type paging is relative to PageNumberPagination The point is , It avoids artificial in url You can refresh the page by passing in the parameters ( because url Irregular ), The disadvantages are also obvious. You can only turn the page up and down .
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