Fixed #2655 -- added documentation about resolve_variable() for custom template
tags. Thanks dave@thebarproject.com. git-svn-id: http://code.djangoproject.com/svn/django/trunk@4477 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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AUTHORS
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AUTHORS
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@ -66,6 +66,7 @@ answer newbie questions, and generally made Django that much better:
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Matt Croydon <http://www.postneo.com/>
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Matt Croydon <http://www.postneo.com/>
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dackze+django@gmail.com
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dackze+django@gmail.com
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Jonathan Daugherty (cygnus) <http://www.cprogrammer.org/>
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Jonathan Daugherty (cygnus) <http://www.cprogrammer.org/>
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dave@thebarproject.com
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Jason Davies (Esaj) <http://www.jasondavies.com/>
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Jason Davies (Esaj) <http://www.jasondavies.com/>
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Alex Dedul
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Alex Dedul
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deric@monowerks.com
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deric@monowerks.com
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@ -801,6 +801,70 @@ Python 2.4 and above::
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If you leave off the ``name`` argument, as in the second example above, Django
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If you leave off the ``name`` argument, as in the second example above, Django
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will use the function's name as the tag name.
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will use the function's name as the tag name.
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Passing template variables to the tag
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Although you can pass any number of arguments to a template tag using
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``token.split_contents()``, the arguments are all unpacked as
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string literals. A little more work is required in order to dynamic content (a
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template variable) to a template tag as an argument.
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While the previous examples have formatted the current time into a string and
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returned the string, suppose you wanted to pass in a ``DateTimeField`` from an
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object and have the template tag format that date-time::
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<p>This post was last updated at {% format_time blog_entry.date_updated "%Y-%m-%d %I:%M %p" %}.</p>
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Initially, ``token.split_contents()`` will return three values:
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1. The tag name ``format_time``.
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2. The string "blog_entry.date_updated" (without the surrounding quotes).
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3. The formatting string "%Y-%m-%d %I:%M %p". The return value from
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``split_contents()`` will include the leading and trailing quotes for
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string literals like this.
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Now your tag should begin to look like this::
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from django import template
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def do_format_time(parser, token):
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try:
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# split_contents() knows not to split quoted strings.
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tag_name, date_to_format, format_string = token.split_contents()
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except ValueError:
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raise template.TemplateSyntaxError, "%r tag requires exactly two arguments" % token.contents[0]
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if not (format_string[0] == format_string[-1] and format_string[0] in ('"', "'")):
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raise template.TemplateSyntaxError, "%r tag's argument should be in quotes" % tag_name
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return FormatTimeNode(date_to_format, format_string[1:-1])
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You also have to change the renderer to retrieve the actual contents of the
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``date_updated`` property of the ``blog_entry`` object. This can be
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accomplished by using the ``resolve_variable()`` function in
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``django.template``. You pass ``resolve_variable()`` the variable name and the
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current context, available in the ``render`` method::
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from django import template
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from django.template import resolve_variable
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import datetime
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class FormatTimeNode(template.Node):
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def __init__(self, date_to_format, format_string):
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self.date_to_format = date_to_format
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self.format_string = format_string
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def render(self, context):
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try:
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actual_date = resolve_variable(self.date_to_format, context)
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return actual_date.strftime(self.format_string)
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except VariableDoesNotExist:
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return ''
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``resolve_variable`` will try to resolve ``blog_entry.date_updated`` and then
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format it accordingly.
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.. note::
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The ``resolve_variable()`` function will throw a ``VariableDoesNotExist``
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exception if it cannot resolve the string passed to it in the current
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context of the page.
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Shortcut for simple tags
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Shortcut for simple tags
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~~~~~~~~~~~~~~~~~~~~~~~~
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~~~~~~~~~~~~~~~~~~~~~~~~
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