77 lines
3.0 KiB
Python
77 lines
3.0 KiB
Python
from copy import copy
|
|
from math import ceil
|
|
|
|
class InvalidPage(Exception):
|
|
pass
|
|
|
|
class ObjectPaginator:
|
|
"""
|
|
This class makes pagination easy. Feed it a module (an object with
|
|
get_count() and get_list() methods) and a dictionary of arguments
|
|
to be passed to those methods, plus the number of objects you want
|
|
on each page. Then read the hits and pages properties to see how
|
|
many pages it involves. Call get_page with a page number (starting
|
|
at 0) to get back a list of objects for that page.
|
|
|
|
Finally, check if a page number has a next/prev page using
|
|
has_next_page(page_number) and has_previous_page(page_number).
|
|
"""
|
|
def __init__(self, module, args, num_per_page, count_method='get_count', list_method='get_list'):
|
|
self.module, self.args = module, args
|
|
self.num_per_page = num_per_page
|
|
self.count_method, self.list_method = count_method, list_method
|
|
self._hits, self._pages = None, None
|
|
self._has_next = {} # Caches page_number -> has_next_boolean
|
|
|
|
def get_page(self, page_number):
|
|
try:
|
|
page_number = int(page_number)
|
|
except ValueError:
|
|
raise InvalidPage
|
|
if page_number < 0:
|
|
raise InvalidPage
|
|
args = copy(self.args)
|
|
args['offset'] = page_number * self.num_per_page
|
|
# Retrieve one extra record, and check for the existence of that extra
|
|
# record to determine whether there's a next page.
|
|
args['limit'] = self.num_per_page + 1
|
|
object_list = getattr(self.module, self.list_method)(**args)
|
|
if not object_list:
|
|
raise InvalidPage
|
|
self._has_next[page_number] = (len(object_list) > self.num_per_page)
|
|
return object_list[:self.num_per_page]
|
|
|
|
def has_next_page(self, page_number):
|
|
"Does page $page_number have a 'next' page?"
|
|
if not self._has_next.has_key(page_number):
|
|
if self._pages is None:
|
|
args = copy(self.args)
|
|
args['offset'] = (page_number + 1) * self.num_per_page
|
|
args['limit'] = 1
|
|
object_list = getattr(self.module, self.list_method)(**args)
|
|
self._has_next[page_number] = (object_list != [])
|
|
else:
|
|
self._has_next[page_number] = page_number < (self.pages - 1)
|
|
return self._has_next[page_number]
|
|
|
|
def has_previous_page(self, page_number):
|
|
return page_number > 0
|
|
|
|
def _get_hits(self):
|
|
if self._hits is None:
|
|
order_args = copy(self.args)
|
|
if order_args.has_key('ordering_tuple'):
|
|
del order_args['ordering_tuple']
|
|
if order_args.has_key('select_related'):
|
|
del order_args['select_related']
|
|
self._hits = getattr(self.module, self.count_method)(**order_args)
|
|
return self._hits
|
|
|
|
def _get_pages(self):
|
|
if self._pages is None:
|
|
self._pages = int(ceil(self.hits / float(self.num_per_page)))
|
|
return self._pages
|
|
|
|
hits = property(_get_hits)
|
|
pages = property(_get_pages)
|