Template Tags for Time Branching: ifbefore, ifafter, ifafterbefore
2011-09-10 20:20 (13 years ago)
ytyng
# -*- coding: utf-8 -*-
"""
Template tag to determine and display based on time
Example:
{% ifbefore '2011-12-24 20:00:00' %}
This is displayed before 2011-12-24 20:00:00
{% else %}
This is displayed after 2011-12-24 20:00:00
{% endifbefore %}
Arguments can be datetime or date strings in the formats
'%Y-%m-%d %H:%M:%S', '%Y-%m-%d', '%H:%M:%S'
"""
import datetime
from django import template
from django.template import Node, NodeList, resolve_variable
register = template.Library()
class IfAfterBeforeNode(Node):
child_nodelists = ('nodelist_true', 'nodelist_false')
datestr_format_list = ('%Y-%m-%d %H:%M:%S', '%Y-%m-%d', '%H:%M:%S')
def __init__(self, var_after, var_before, nodelist_true, nodelist_false=None):
self.nodelist_true, self.nodelist_false = nodelist_true, nodelist_false
self.var_after = var_after
self.var_before = var_before
self.now = datetime.datetime.now()
def strptime(self, date_string):
"""
Parse date string into datetime.
Returns None if parsing fails.
"""
date_string = date_string.strip("""'" """)
for datestr_format in self.datestr_format_list:
try:
return datetime.datetime.strptime(date_string, datestr_format)
except ValueError:
pass
return None
def __repr__(self):
return "<IfBeforeAfter node>"
def __iter__(self):
for node in self.nodelist_true:
yield node
for node in self.nodelist_false:
yield node
def arg_to_dt_or_none(self, arg, context):
"""
Retrieve argument as datetime or none
Used for self.var_after, self.var_before
"""
if not arg:
return None
try:
# Argument may be datetime
dt = resolve_variable(arg, context)
except template.VariableDoesNotExist:
dt = None
if dt is None or not isinstance(dt, datetime.datetime):
dt = self.strptime(arg)
return dt
def render(self, context):
dt_after = self.arg_to_dt_or_none(self.var_after, context)
dt_before = self.arg_to_dt_or_none(self.var_before, context)
if dt_after and dt_before:
if dt_after <= self.now < dt_before:
return self.nodelist_true.render(context)
else:
return self.nodelist_false.render(context)
elif dt_after:
if dt_after <= self.now:
return self.nodelist_true.render(context)
else:
return self.nodelist_false.render(context)
elif dt_before:
if self.now < dt_before:
return self.nodelist_true.render(context)
else:
return self.nodelist_false.render(context)
else:
return u'Parse Error. No after, before'
@register.tag
def ifbefore(parser, token):
"""
Render if current time is before "YYYY-MM-DD HH:MM:SS"
"""
_tagname, var_before = token.split_contents()
nodelist_true = parser.parse(('else', 'endifbefore'))
token = parser.next_token()
if token.contents == 'else':
nodelist_false = parser.parse(('endifbefore',))
parser.delete_first_token()
else:
nodelist_false = NodeList()
return IfAfterBeforeNode(None, var_before, nodelist_true, nodelist_false)
@register.tag
def ifafter(parser, token):
"""
Render if current time is after "YYYY-MM-DD HH:MM:SS"
"""
_tagname, var_after = token.split_contents()
nodelist_true = parser.parse(('else', 'endifafter'))
token = parser.next_token()
if token.contents == 'else':
nodelist_false = parser.parse(('endifafter',))
parser.delete_first_token()
else:
nodelist_false = NodeList()
return IfAfterBeforeNode(var_after, None, nodelist_true, nodelist_false)
@register.tag
def ifafterbefore(parser, token):
"""
Take two arguments and render if the current time is between them
"""
_tagname, var_after, var_before = token.split_contents()
nodelist_true = parser.parse(('else', 'endifafterbefore'))
token = parser.next_token()
if token.contents == 'else':
nodelist_false = parser.parse(('endifafterbefore',))
parser.delete_first_token()
else:
nodelist_false = NodeList()
return IfAfterBeforeNode(var_after, var_before, nodelist_true, nodelist_false)
The author runs the application development company Cyberneura.
We look forward to discussing your development needs.
We look forward to discussing your development needs.