我对这个解决方案并不完全满意，它可能会破坏使用Request 的提要，并且取决于一种神奇的方法。就这样：
#coding:utf-8
# Author: Armando Pérez Marqués <mandx@rbol.org>
# Purpose: Django TemplateTag to output feed links in templates in a DRY way
# Created: 05/07/2010
import re
from django import template
from django.conf import settings
from django.contrib.syndication.views import Feed
from django.core.urlresolvers import reverse, resolve, NoReverseMatch
from django.template import Node
from django.template import TemplateSyntaxError
from django.utils.encoding import smart_str
from django.utils.html import escape as html_escape
from django.utils.safestring import mark_safe
register = template.Library()
kwarg_re = re.compile(r"(?:(\w+)=)?(.+)")
class FeedInfoNode(Node):
def __init__(self, view_name, args, kwargs, asvar):
self.view_name = view_name
self.args = args
self.kwargs = kwargs
self.asvar = asvar
def render(self, context):
args = [arg.resolve(context) for arg in self.args]
kwargs = dict([(smart_str(k,'ascii'), v.resolve(context))
for k, v in self.kwargs.items()])
# Try to look up the URL twice: once given the view name, and again
# relative to what we guess is the "main" app. If they both fail,
# re-raise the NoReverseMatch unless we're using the
# {% feed_info ... as var %} construct in which cause return nothing.
url = ''
try:
url = reverse(self.view_name, args=args, kwargs=kwargs, current_app=context.current_app)
except NoReverseMatch, e:
if settings.SETTINGS_MODULE:
project_name = settings.SETTINGS_MODULE.split('.')[0]
try:
url = reverse(project_name + '.' + self.view_name,
args=args, kwargs=kwargs, current_app=context.current_app)
except NoReverseMatch:
if self.asvar is None:
# Re-raise the original exception, not the one with
# the path relative to the project. This makes a
# better error message.
raise e
else:
if self.asvar is None:
raise e
if 'request' in context:
request = context['request']
else:
request = None
feed_instance, feed_args, feed_kwargs = resolve(url)
if not isinstance(feed_instance, Feed):
raise NoReverseMatch, \
'feed_info can only reverse class-based feeds'
feed_obj = feed_instance.get_object(request, *feed_args, **feed_kwargs)
feed_data = {
'url': url,
'obj': feed_instance,
'args': feed_args,
'kwargs': feed_kwargs,
#'title': html_escape(feed_instance.__get_dynamic_attr('title', obj)),
'title': html_escape(
feed_instance._Feed__get_dynamic_attr('title', feed_obj)
),
'type': feed_instance.feed_type.mime_type,
}
if self.asvar:
context[self.asvar] = feed_data
return ''
else:
return mark_safe(
'<link rel="alternate" type="%(type)s" title="%(title)s" href="%(url)s" />' \
% feed_data
)
def feed_info(parser, token):
"""
Returns an mapping containing populated info about the reversed feed
Works exactly as the url tag, but the mapping is not returned, instead
a variable is always set in the context.
This is a way to define links that aren't tied to a particular URL
configuration::
{% feed_info path.to.some_feed_view_class arg1 arg2 as feed_info_var %}
or
{% feed_info path.to.some_feed_view_class name1=value1 name2=value2 as feed_info_var %}
"""
bits = token.split_contents()
if len(bits) < 2:
raise TemplateSyntaxError("'%s' takes at least one argument"
" (path to a feed view)" % bits[0])
viewname = bits[1]
args = []
kwargs = {}
asvar = None
bits = bits[2:]
if len(bits) >= 2 and bits[-2] == 'as':
asvar = bits[-1]
bits = bits[:-2]
# Backwards compatibility: check for the old comma separated format
# {% url urlname arg1,arg2 %}
# Initial check - that the first space separated bit has a comma in it
if bits and ',' in bits[0]:
check_old_format = True
# In order to *really* be old format, there must be a comma
# in *every* space separated bit, except the last.
for bit in bits[1:-1]:
if ',' not in bit:
# No comma in this bit. Either the comma we found
# in bit 1 was a false positive (e.g., comma in a string),
# or there is a syntax problem with missing commas
check_old_format = False
break
else:
# No comma found - must be new format.
check_old_format = False
if check_old_format:
# Confirm that this is old format by trying to parse the first
# argument. An exception will be raised if the comma is
# unexpected (i.e. outside of a static string).
match = kwarg_re.match(bits[0])
if match:
value = match.groups()[1]
try:
parser.compile_filter(value)
except TemplateSyntaxError:
bits = ''.join(bits).split(',')
# Now all the bits are parsed into new format,
# process them as template vars
if len(bits):
for bit in bits:
match = kwarg_re.match(bit)
if not match:
raise TemplateSyntaxError("Malformed arguments to url tag")
name, value = match.groups()
if name:
kwargs[name] = parser.compile_filter(value)
else:
args.append(parser.compile_filter(value))
return FeedInfoNode(viewname, args, kwargs, asvar)
feed_info = register.tag(feed_info)
我从{% url %}模板标签的代码开始，然后在获取到feed的URL后，使用resolve()获取Feed子类实例，然后获取需要的属性。
注意事项
- 需要 Django 1.2 类提要，不知道如何使用旧的提要方式。
- 如果提要类使用请求对象，则必须配置
request context processor，因为如果上下文中不存在None，则会传递它。
- Feed.__get_dynamic_attr() 有点奇怪。 Feed 子类实例没有这个方法；相反，它以另一个名称出现。不知道如何在运行时找出名称...