On May 13, 2006, at 4:30 PM, nevroe wrote:
> The Django documentation here [1] says something about it being very
> useful that Context objects are stacks.
>
> [1]: http://www.djangoproject.com/documentation/templates_python/
>
> """
> A Context object is a stack. That is, you can push() and pop() it. If
> you pop() too much, it'll raise django.template.ContextPopException:
> ...
> Using a Context as a stack comes in handy in some custom template
> tags,
> as you'll see below.
> """
>
> I'm trying to figure out the case scenario where this becomes a useful
> thing, and I couldn't find the mentioned documentation. Did I miss
> it,
> or does anyone have a good example where it is useful to have template
> context as a stack?
Well, the canonical example is ``{% for %}`` loops::
{% for var in list %}
{{ var }}
{% endfor %}
It wouldn't make any sense if ``{{ var }}`` became available outside
of the ``{% for %}`` loop or (even worse) overwrote an existing
variable.
So if you ever want to write a block tag that binds variables, then
you'll want to be pushing/popping contexts.
Jacob
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