Fixed #4534 -- Added an "else" option to the "ifchanged" template tag.

Patch from SmileyChris.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8095 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/template/defaulttags.py

@@ -157,8 +157,8 @@ class ForNode(Node):
         return nodelist.render(context)
 
 class IfChangedNode(Node):
-    def __init__(self, nodelist, *varlist):
+    def __init__(self, nodelist_true, nodelist_false, *varlist):
-        self.nodelist = nodelist
+        self.nodelist_true, self.nodelist_false = nodelist_true, nodelist_false
         self._last_seen = None
         self._varlist = map(Variable, varlist)
         self._id = str(id(self))
@@ -173,20 +173,21 @@ class IfChangedNode(Node):
                 # like an OR evaluation of the multiple variables.
                 compare_to = [var.resolve(context) for var in self._varlist]
             else:
-                compare_to = self.nodelist.render(context)
+                compare_to = self.nodelist_true.render(context)
         except VariableDoesNotExist:
             compare_to = None
 
-        if  compare_to != self._last_seen:
+        if compare_to != self._last_seen:
             firstloop = (self._last_seen == None)
             self._last_seen = compare_to
             context.push()
             context['ifchanged'] = {'firstloop': firstloop}
-            content = self.nodelist.render(context)
+            content = self.nodelist_true.render(context)
             context.pop()
             return content
-        else:
+        elif self.nodelist_false:
-            return ''
+            return self.nodelist_false.render(context)
+        return ''
 
 class IfEqualNode(Node):
     def __init__(self, var1, var2, nodelist_true, nodelist_false, negate):
@@ -803,9 +804,14 @@ def ifchanged(parser, token):
             {% endfor %}
     """
     bits = token.contents.split()
-    nodelist = parser.parse(('endifchanged',))
+    nodelist_true = parser.parse(('else', 'endifchanged'))
-    parser.delete_first_token()
+    token = parser.next_token()
-    return IfChangedNode(nodelist, *bits[1:])
+    if token.contents == 'else':
+        nodelist_false = parser.parse(('endifchanged',))
+        parser.delete_first_token()
+    else:
+        nodelist_false = NodeList()
+    return IfChangedNode(nodelist_true, nodelist_false, *bits[1:])
 ifchanged = register.tag(ifchanged)
 
 #@register.tag

docs/templates.txt

@@ -828,6 +828,19 @@ The 'ifchanged' block tag is used within a loop. It has two possible uses.
             {% endifchanged %}
         {% endfor %}
 
+The ``ifchanged`` tag also takes an optional ``{% else %}`` clause that will
+be displayed if the value has not changed::
+
+    {% for match in matches %}
+        <div style="background-color:
+            {% ifchanged match.ballot_id %}
+                {% cycle red,blue %}
+            {% else %}
+                grey
+            {% endifchanged %}
+        ">{{ match }}</div>
+    {% endfor %}
+
 ifequal
 ~~~~~~~
 

tests/regressiontests/templates/tests.py

@@ -565,6 +565,14 @@ class Templates(unittest.TestCase):
             # ifchanged for the day.
             'ifchanged-param04': ('{% for d in days %}{% ifchanged d.day %}{{ d.day }}{% endifchanged %}{% for h in d.hours %}{% ifchanged d.day h %}{{ h }}{% endifchanged %}{% endfor %}{% endfor %}', {'days':[{'day':1, 'hours':[1,2,3]},{'day':2, 'hours':[3]},] }, '112323'),
 
+            # Test the else clause of ifchanged.
+            'ifchanged-else01': ('{% for id in ids %}{{ id }}{% ifchanged id %}-first{% else %}-other{% endifchanged %},{% endfor %}', {'ids': [1,1,2,2,2,3]}, '1-first,1-other,2-first,2-other,2-other,3-first,'),
+
+            'ifchanged-else02': ('{% for id in ids %}{{ id }}-{% ifchanged id %}{% cycle red,blue %}{% else %}grey{% endifchanged %},{% endfor %}', {'ids': [1,1,2,2,2,3]}, '1-red,1-grey,2-blue,2-grey,2-grey,3-red,'),
+            'ifchanged-else03': ('{% for id in ids %}{{ id }}{% ifchanged id %}-{% cycle red,blue %}{% else %}{% endifchanged %},{% endfor %}', {'ids': [1,1,2,2,2,3]}, '1-red,1,2-blue,2,2,3-red,'),
+
+            'ifchanged-else04': ('{% for id in ids %}{% ifchanged %}***{{ id }}*{% else %}...{% endifchanged %}{{ forloop.counter }}{% endfor %}', {'ids': [1,1,2,2,2,3,4]}, '***1*1...2***2*3...4...5***3*6***4*7'),
+
             ### IFEQUAL TAG ###########################################################
             'ifequal01': ("{% ifequal a b %}yes{% endifequal %}", {"a": 1, "b": 2}, ""),
             'ifequal02': ("{% ifequal a b %}yes{% endifequal %}", {"a": 1, "b": 1}, "yes"),