#18651: Assignment tags should allow optional assignments
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Reporter: mitar | Owner: nobody
Type: New feature | Status: closed
Component: Template system | Version: 1.4
Severity: Normal | Resolution: needsinfo
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 1 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by tim_heap):
I can think of two main use-cases for this, and two problems it solves.
One of these use-cases has already been encountered in the built in tags,
as documented below, so the problem it solves is real.
Firstly, when a sensible default name exists for a tag, but you may want
to change it. Consider a tag `{% get_comments_for object %}`, which find
all comments against the object passed in, and assigns the result to the
`comments` variable in the template. If you have two objects on the page,
and want to get the comments from both, the names would collide. In this
case, you could use `{% get_comments_for foo as foo_comments %}` and `{%
get_comments_for bar as bar_comments %}`.
The second use case is assigning or outputting the result. This is already
used by the built in `{% url %}` tag. You can use `{% url foo %}` to print
the URL directly, or `{% url foo as foo_url %}` to assign it to the `foo`
variable in the template.
This could be implemented as either two new decorators:
{{{
@register.assignment_tag_with_default(default='comments')
def get_comments_for(object):
pass
@register.optional_assignment_tag()
def url(name, *args, **kwargs):
pass
}}}
or as options on the existing decorator
{{{
@register.assignment_tag(default_name='comments')
def get_comments_for(object):
pass
@register.assignment_tag(optional_assignment=True)
def url(name, *args, **kwargs):
pass
}}}
In the second case of extending the current decorator, `default_name` and
`optional_assignment` would have to be mutually exclusive.
--
Ticket URL: <https://code.djangoproject.com/ticket/18651#comment:3>
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