Question

Is there a way to maintain state between tag calls? I need to store the last item passed to a tag that I have created. It appeared as if I could use context to do this, but it doesn’t seem to work. Here is my code:

@register.simple_tag(takes_context=True)
def date_divider(context, date):
    if 'last_date' not in context or context['last_date'] != date:
        # display new date header
        context['last_date'] = date
    return date_header

The problem is that a new date header is always created even if the date passed in should match the date in the context.

I’m guessing I’m using context wrong here… Is there a way to store this last date in the context or is there a better way to do this?

Answer 1

It seems likely that the context into which you are entering last_date no longer exists the second time you reach this tag (for instance, perhaps that context has been popped already?). A (sort of hackish) solution is to be sure that you insert last_date into the “highest” context:

if 'last_date' not in context.dicts[0] or context.dicts[0]['last_date'] != date:
    context.dicts[0]['last_date'] = date

This kind of approach is often needed when the tags that you are writing aren’t “nested”, I’ve found. Incidentally, I’ve also found that tags of this sort are themselves often a hack!

(Not to say this particular case is, just that my cases have been).