1 from django.template import Library, Node, TemplateSyntaxError

     2 from django.template import resolve_variable

     3 from django.core.cache import cache

     4 from django.utils.encoding import force_unicode

     5 

     6 register = Library()

     7 

     8 class CacheNode(Node):

     9     def __init__(self, nodelist, expire_time, fragment_name, vary_on):

    10         self.nodelist = nodelist

    11         self.expire_time = expire_time

    12         self.fragment_name = fragment_name

    13         self.vary_on = vary_on

    14 

    15     def render(self, context):

    16         # Build a unicode key for this fragment and all vary-on's.

    17         cache_key = u':'.join([self.fragment_name] + \

    18             [force_unicode(resolve_variable(var, context)) for var in self.vary_on])

    19         value = cache.get(cache_key)

    20         if value is None:

    21             value = self.nodelist.render(context)

    22             cache.set(cache_key, value, self.expire_time)

    23         return value

    24 

    25 def do_cache(parser, token):

    26     """

    27     This will cache the contents of a template fragment for a given amount

    28     of time.

    29 

    30     Usage::

    31 

    32         {% load cache %}

    33         {% cache [expire_time] [fragment_name] %}

    34             .. some expensive processing ..

    35         {% endcache %}

    36 

    37     This tag also supports varying by a list of arguments::

    38 

    39         {% load cache %}

    40         {% cache [expire_time] [fragment_name] [var1] [var2] .. %}

    41             .. some expensive processing ..

    42         {% endcache %}

    43 

    44     Each unique set of arguments will result in a unique cache entry.

    45     """

    46     nodelist = parser.parse(('endcache',))

    47     parser.delete_first_token()

    48     tokens = token.contents.split()

    49     if len(tokens) < 3:

    50         raise TemplateSyntaxError(u"'%r' tag requires at least 2 arguments." % tokens[0])

    51     try:

    52         expire_time = int(tokens[1])

    53     except ValueError:

    54         raise TemplateSyntaxError(u"First argument to '%r' must be an integer (got '%s')." % (tokens[0], tokens[1]))

    55     return CacheNode(nodelist, expire_time, tokens[2], tokens[3:])

    56 

    57 register.tag('cache', do_cache)