from django.template import Library, Node, TemplateSyntaxError
from django.utils.encoding import smart_unicode
register = Library()
class FirstNotNoneNode(Node):
def __init__(self, vars):
self.vars = vars
def render(self, context):
for var in self.vars:
value = var.resolve(context, True)
if value is not None:
return smart_unicode(value)
return u''
def firstnotnone(parser,token):
"""
Outputs the first variable passed that is not None
"""
bits = token.split_contents()[1:]
if len(bits) < 1:
raise TemplateSyntaxError("'firstnotnone' statement requires at least one argument")
return FirstNotNoneNode([parser.compile_filter(bit) for bit in bits])
firstnotnone = register.tag(firstnotnone)
firstof
标记不是通过simple_tag
修饰符实现的,它使用template.Node
子类的长形式和一个单独的标记函数。您可以在django.template.defaulttags
中看到代码-为了您的目的更改它应该相当简单。在自定义模板标记:
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