Re: NameMapper issues with Google App Engine db.Model objects

On Sat, 14 Aug 2010, Chad George wrote:

> In AppEngine, db.Model objects unfortunately implement a "has_key()"
> method that checks if a model instance has had a key assigned to it
> yet.
> 
> This causes NameMapper.py to determine that it should use dictionary
> style access instead of getattr().


I /think/ you can circumvent this functionality by disabling autocalling, I've
not used AppEngine, but you might try that:

http://cheetahtemplate.org/docs/users_guide_html_multipage/language.namemapper.autocalling.html




> 
> I think there are two possible solutions:
>  1. use hasattr(obj, "keys") instead of hasattr(obj, "has_key")
>  2. try to use hasattr()/getattr() ... before trying dictionary access
> 
> I tested #1 and it seems to work...but I'm too new to Cheetah to know
> if there are unintended consequences
> 
> For #2 the biggest issue I see is in _valueForName() ... you
> definitely don't want to hit the exception on every access to a
> dictionary, so you'd need another call to hasattr()  ... which
> presumably was just done before getting to _valueForName() in the
> first place.
> 
> Probably not a big deal either way. I'm not sure if there was a
> pre-existing design decision to try dictionary access before attribute
> access.
> 
> - Chad
> 
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Cheers,
-R. Tyler Ballance
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