My apologies, this was intended to be posted to the Django users group. On Thursday, 11 July 2013 21:54:25 UTC+1, Tom Christie wrote: > > I've noted that the generic view implementations use the private `_clone` > method when returning the queryset > attribute<https://github.com/django/django/blob/master/django/views/generic/detail.py#L72> > . > > Presumably the need for that is something to do with the potential for > querysets to be cached or otherwise incorrectly stateful if this cloning > isn't performed. What's confusing me is that it's not at all obvious > *exactly* what the implications of making (or failing to make) this call > are. > > Furthermore if it *is* something that's strictly required in this > circumstance then do we need to be documenting whatever behavior is being > triggered, so that developers writing their own class based views don't > make the (mistake?) of simply returning/using a queryset attribute without > having first cloned it? > > For example, is the following incorrect? > > class SomeBaseGenericView(View): > queryset = None > > def get_queryset(self): > """ > Simply return `.queryset` by default. Subclasses may override > this behavior. > """ > return self.queryset > > If so, under what set of conditions can it fail, and is it possible to > unit test for the failing behavior? > > I've dug into the source, but the `_clone` method isn't documented, nor > can I find anything terribly helpful related to queryset cloning after > googling around for a while. > > Many thanks, > > Tom > >
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