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from django.template import Library, Node, TemplateSyntaxError, Variable, VariableDoesNotExist
from django.template import resolve_variable
from django.core.cache import cache
from django.utils.encoding import force_unicode
register = Library()
class CacheNode(Node):
def __init__(self, nodelist, expire_time_var, fragment_name, vary_on):
self.nodelist = nodelist
self.expire_time_var = Variable(expire_time_var)
self.fragment_name = fragment_name
self.vary_on = vary_on
def render(self, context):
try:
expire_time = self.expire_time_var.resolve(context)
except VariableDoesNotExist:
raise TemplateSyntaxError('"cache" tag got an unknkown variable: %r' % self.expire_time_var.var)
try:
expire_time = int(expire_time)
except (ValueError, TypeError):
raise TemplateSyntaxError('"cache" tag got a non-integer timeout value: %r' % expire_time)
# Build a unicode key for this fragment and all vary-on's.
cache_key = u':'.join([self.fragment_name] + [force_unicode(resolve_variable(var, context)) for var in self.vary_on])
value = cache.get(cache_key)
if value is None:
value = self.nodelist.render(context)
cache.set(cache_key, value, expire_time)
return value
def do_cache(parser, token):
"""
This will cache the contents of a template fragment for a given amount
of time.
Usage::
{% load cache %}
{% cache [expire_time] [fragment_name] %}
.. some expensive processing ..
{% endcache %}
This tag also supports varying by a list of arguments::
{% load cache %}
{% cache [expire_time] [fragment_name] [var1] [var2] .. %}
.. some expensive processing ..
{% endcache %}
Each unique set of arguments will result in a unique cache entry.
"""
nodelist = parser.parse(('endcache',))
parser.delete_first_token()
tokens = token.contents.split()
if len(tokens) < 3:
raise TemplateSyntaxError(u"'%r' tag requires at least 2 arguments." % tokens[0])
return CacheNode(nodelist, tokens[1], tokens[2], tokens[3:])
register.tag('cache', do_cache)
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