Lightning talk from DjangoCon.eu

1. Making
TemplateTags
Suck Less

2. class BadgeCountNode(template.Node):
@classmethod
def handle_token(cls, parser, token):
bits = token.split_contents()
if len(bits) == 2:
return cls(bits[1])
elif len(bits) == 4:
if bits[2] != "as":
raise template.TemplateSyntaxError("Second argument to %r must "
"be 'as'" % bits[0])
return cls(bits[1], bits[3])
raise template.TemplateSyntaxError("%r takes either 1 or 3 arguments." % bits[0])
def __init__(self, user, context_var=None):
self.user = template.Variable(user)
self.context_var = context_var
def render(self, context):
user = self.user.resolve(context)
badge_count = BadgeAward.objects.filter(user=user).count()
if self.context_var is not None:
context[self.context_var] = badge_count
return ""
return unicode(badge_count)
@register.tag
def badge_count(parser, token):
"""
Returns badge count for a user, valid usage is::
{% badge_count user %}
or
{% badge_count user as badges %}
"""
return BadgeCountNode.handle_token(parser, token)

3. WTF is all that crap
50% boilerplate
45 LOC for 4 lines of logic
Hacking parsing

4. There’s gotta be a
better way
A syntax to define argument parsing, how to
parse them, and what types to interpret them
as.
Automatic variable resolution in the context,
and conversion to correct types.

5. django-templatetag-
sugar
Define your templatetags’ syntax in a
Pythonic way
write a function and decorate

6. @tag(register, [Variable(), Optional([Constant("as"), Name()]))
def badge_count(context, user, varname=None):
badge_count = BadgeAward.objects.filter(user=user).count()
if varname is not None:
context[varname] = badge_count
return ""
return unicode(badge_count)
All Done

7. 6 LOC
This feels like cheating...

8. http://github.com/alex/django-templatetag-
sugar
http://alexgaynor.net/
Slides will be on my blog.