On Tue, Oct 23, 2012 at 6:52 PM, Andrew Ingram <andrewof...@gmail.com>wrote:
> Hi all,
>
> This one stung me today. Basically as part of an event (calendar) app, I
> have functionality for splitting a series of events into two at a given
> timestamp. The details aren't particularly relevant, but the key thing is
> that I had a method called "split" on one of the models.
>
> This was working fine until I tried to add a ManyToManyField to the same
> model, at which point it through a rather ugly error during initialisation
> of the apps.
>
> django/db/models/fields/related.py line 56, in add_lazy_relation
>> app_label, model_name = relation.split(".")
>> TypeError: unbound method split() must be called with RecurringEvent
>> instance as first argument (got str instance instead)
>
>
> Because I had no knowledge of the inner workings here, this error wasn't
> helpful until pdb told me that `relation` was an instance of my model. The
> issue is that in this point in the code, relation can either be a model or
> a string 'app_label.model_name', so it's using the presence of a split
> function to determine which it is, me having a split function on my model
> breaks this check. Having a non-callable 'split' causes a similar problem,
> just with a different exception.
>
> Long story short, adding a 'split' method to my model caused the
> inner-workings of Django to break, I think the documentation should provide
> a list of attribute names that can't be added to a Django model without
> breaking things, though this is the first time I've ever come across such a
> problem so it might be a one-off.
>
> Hi Andrew,
Thanks for that gnarly bug report. I'm a little surprised that the 'split'
name causes a problem here; based on my knowledge of Django's internals, I
wouldn't have thought that the situation you describe shouldn't be a
problem. My gut reaction tells me that the actual problem is somewhere else
in your model definition, causing the wrong object instance to be passed
into the 'relation' variable; the 'split' method is a symptom, rather than
the actual problem. However, I may be wrong.
If you can open a bug report with a complete working (or rather, broken)
example of the problem, we can dig into it more. If you're right that the
split method is the problem, we should certainly document it; if the
problem lies somewhere else, there's possibly some better validation that
we need to do.
Yours,
Russ Magee %-)
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