Look at the way contexts are implemented. There are actually a chain of
mappings, and if a variable isn't found in the mapping at the head of the
chain, the next is consulted, and so on. Certain operations (and, apparently,
ifequal is one of them) push a new mapping onto the chain, so when that
tag is closed, and the chain is popped, you have the old "context" back.
Generally, that's a really good thing.
You can, yourself, crawl up the chain of dictionaries, and set the value in
an outer context. This is not a supported interface as far as I can tell, so
your code could stop working in the future. For the simple case you give,
where there is (I presume) only one context pushed between where you
are and point of usage, you could say (in your tag code):
context.dicts[1][var_name] = new_value
(Untested, and you probably want to check for whether there is more than
one element in context.dicts first.)
More complexly, you could find the nearest enclosing scope if which the variable
is set:
for d in context.dicts:
if var_name in d"
d[var_name] = new_value
break
But think about whether you really want to effect to extend to an
arbitrarily higher
scope. You may have a particular case in mind where this if fine, but if you're
making a tag, you probably have an idea that it may be more generally useful.
Perhaps you want to make two tags, one of which defines the context level at
which your other tag has effect.
All still dependent on context internals (though I notice that the
dicts attribute of
contexts doesn't have a leading underscore, so maybe it's intended that you
can access it).
Bill
On Thu, Mar 18, 2010 at 10:40 AM, taniman <the_po...@hotmail.com> wrote:
> I have am using a django custom tag to change the value of a variable.
> But if I change the value in an if tag or a for tag after the end of
> the if/for tag django will show me the old value of the variable. Is
> there something I can do about this?
>
> {% for %}
> {{ varname }} --> output is 50
> {% ifequal somevalues %}
> {% changevariable varname 10 %}
> {{ varname }} --> this output is 10
>
> {% endifequal %}
> {{ varname }} --> out is 50 instead of 10.
> {% endfor %}
>
>
> I use this code(just a small snippet):
>
> def render(self, context):
>
> context[varname] = newvalue
> return ' '
>
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