c4urself · June 16, 2011 08:39 · Jun 16, 2011 · Jun 16, 2011
diff --git a/url_patterns.py b/url_patterns.py
@@ -1,4 +1,3 @@
-
 (r'^articles/(?P<year>\d{4}/?$, 'main.views.year'),
 
 # When a use case comes up that a month needs to be involved as
@@ -56,8 +55,8 @@
     'changer.socialschools.communities.views.show_recent',
     name="community-recent"),
 
-"""
-This makes the following possible:
+
+# This makes the following possible:
 
 """
 >>> from django.core.urlresolvers import resolve

diff --git a/url_patterns.py b/url_patterns.py
@@ -0,0 +1,86 @@
+
+(r'^articles/(?P<year>\d{4}/?$, 'main.views.year'),
+
+# When a use case comes up that a month needs to be involved as
+# well, you add an argument in your regex:
+
+(r'^articles/(?P<year>\d{4}/(?P<month>\d{2})/?$, 'main.views.year_month'),
+
+# That works fine, unless of course you want to show something
+# different for just the year, in which case the following case can be
+# used, making separate views based on the arguments as djangoproject
+# suggests (http://docs.djangoproject.com/en/dev/topics/http/urls/)
+
+urlpatterns = patterns('',
+    (r'^articles/(?P<year>\d{4})/$', 'news.views.year_archive'),
+    (r'^articles/(?P<year>\d{4})/(?P<month>\d{2})/$', 'news.views.month_archive'),
+    (r'^articles/(?P<year>\d{4})/(?P<month>\d{2})/(?P<day>\d+)/$', 'news.views.article_detail'),
+)
+
+# However it would be nice if we could make one pattern for one
+# view with optional arguments. Luckily the django url reversing
+# engine allows this, and we can do the following:
+
+url(r'''^community/(?P<base_slug>[^/]+)/?(?P<school_slug>[^/]+)?/?(?P<grade_slug>[^/]+)?/?(?P<class_slug>      [^/]+)?$''',
+    'changer.socialschools.posts.views.show_community',
+    name="community"),
+
+# This works fine when calling the url, but reversing will cause a 
+# problem because django will treat the backslashes as optional and
+# not include them in the reversed url, causing munged urls:
+
+# community/base/schoolgradeclass
+
+# To counter this we can alter the regex as follows, by making the
+# '/' dependent on the presence of the corresponding slug. We make
+# sure not to group this by adding (?:) so as not to pollute the
+# django reversing engine with unnecessary arguments and at the 
+# same time keeping the arguments optional:
+
+    url(r'''^community(?:\/(?P<base_slug>[^/]+))'''
+                          r'''(?:\/(?P<school_slug>[^/]+))?'''
+                          r'''(?:\/(?P<grade_slug>[^/]+))?'''
+                          r'''(?:\/(?P<class_slug>[^/]+))?$''',
+       'changer.socialschools.communities.views.this_community',
+       name="community-view"),
+
+# This makes it work with one url pattern. But what if we want to
+# make a pattern for recent news in that a particular community, 
+# such as news in a particular grade or school? We can add an 
+# negative lookahead assertion:
+
+url(r'''^community/(?P<base_slug>[^/]+)'''
+                 r'''(?:\/(?P<school_slug>(?!recent)[^/]+))?'''
+                 r'''(?:\/(?P<grade_slug>(?!recent)[^/]+))?'''
+                 r'''(?:\/(?P<class_slug>(?!recent)[^/]+))?/recent/?$''',
+    'changer.socialschools.communities.views.show_recent',
+    name="community-recent"),
+
+"""
+This makes the following possible:
+
+"""
+>>> from django.core.urlresolvers import resolve
+>>> resolve('/community/base/school/grade/class/recent')
+
+ResolverMatch(func=<function show_recent at 0x103097d70>, args=(), kwargs={'class_slug': 'class', 'base_slug': 'base', 'grade_slug': 'grade', 'school_slug': 'school'}, url_name='community_recent', app_name='None', namespace='')
+"""
+
+# and also:
+
+"""
+>>> resolve('/community/base/school/grade/class')
+
+ResolverMatch(func=<function this_community at 0x10307a500>, args=(), kwargs={'class_slug': 'class', 'base_slug': 'base', 'grade_slug': 'grade', 'school_slug': 'school'}, url_name='community-view', app_name='None', namespace='')
+"""
+
+# So that if we only want news for the school, 'recent' is taken
+# up as a slug for the grade:
+
+"""
+>>> resolve('/community/base/school/recent')
+
+ResolverMatch(func=<function show_recent at 0x1031a50c8>, args=(), kwargs={'class_slug': None, 'base_slug': 'base', 'grade_slug': None, 'school_slug': 'school'}, url_name='community-recent', app_name='None', namespace='')
+
+"""
+
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