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Fixed #6398: added an optional {% empty %} clause to the {% for %} template tag. The contents of this clause are rendered if the list iterated over turns out to be empty. Thanks, Jannis Leidel.

Browse Source 
Astute readers will notice that the patch originally called this `default`; after consideration I decided that `empty` is a very slightly better color for this particular bikeshed.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@9530 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Jacob Kaplan-Moss
2008-11-24 22:01:48 +00:00
parent 136c4f8549
commit 4aa97f5c18
3 changed files with 75 additions and 5 deletions
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48
django/template/defaulttags.py
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@@ -83,10 +83,14 @@ class FirstOfNode(Node):
return u''
class ForNode(Node):
def __init__(self, loopvars, sequence, is_reversed, nodelist_loop):
def __init__(self, loopvars, sequence, is_reversed, nodelist_loop, nodelist_empty=None):
self.loopvars, self.sequence = loopvars, sequence
self.is_reversed = is_reversed
self.nodelist_loop = nodelist_loop
if nodelist_empty is None:
self.nodelist_empty = NodeList()
else:
self.nodelist_empty = nodelist_empty
def __repr__(self):
reversed_text = self.is_reversed and ' reversed' or ''
@@ -97,16 +101,18 @@ class ForNode(Node):
def __iter__(self):
for node in self.nodelist_loop:
yield node
for node in self.nodelist_empty:
yield node
def get_nodes_by_type(self, nodetype):
nodes = []
if isinstance(self, nodetype):
nodes.append(self)
nodes.extend(self.nodelist_loop.get_nodes_by_type(nodetype))
nodes.extend(self.nodelist_empty.get_nodes_by_type(nodetype))
return nodes
def render(self, context):
nodelist = NodeList()
if 'forloop' in context:
parentloop = context['forloop']
else:
@@ -121,6 +127,9 @@ class ForNode(Node):
if not hasattr(values, '__len__'):
values = list(values)
len_values = len(values)
if len_values < 1:
return self.nodelist_empty.render(context)
nodelist = NodeList()
if self.is_reversed:
values = reversed(values)
unpack = len(self.loopvars) > 1
@@ -610,6 +619,30 @@ def do_for(parser, token):
{{ key }}: {{ value }}
{% endfor %}
The ``for`` tag can take an optional ``{% empty %}`` clause that will
be displayed if the given array is empty or could not be found::
<ul>
{% for athlete in athlete_list %}
<li>{{ athlete.name }}</li>
{% empty %}
<li>Sorry, no athletes in this list.</li>
{% endfor %}
<ul>
The above is equivalent to -- but shorter, cleaner, and possibly faster
than -- the following::
<ul>
{% if althete_list %}
{% for athlete in athlete_list %}
<li>{{ athlete.name }}</li>
{% endfor %}
{% else %}
<li>Sorry, no athletes in this list.</li>
{% endif %}
</ul>
The for loop sets a number of variables available within the loop:
========================== ================================================
@@ -646,9 +679,14 @@ def do_for(parser, token):
" %s" % token.contents)
sequence = parser.compile_filter(bits[in_index+1])
nodelist_loop = parser.parse(('endfor',))
parser.delete_first_token()
return ForNode(loopvars, sequence, is_reversed, nodelist_loop)
nodelist_loop = parser.parse(('default', 'endfor',))
token = parser.next_token()
if token.contents == 'default':
nodelist_default = parser.parse(('endfor',))
parser.delete_first_token()
else:
nodelist_default = None
return ForNode(loopvars, sequence, is_reversed, nodelist_loop, nodelist_default)
do_for = register.tag("for", do_for)
def do_ifequal(parser, token, negate):