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

Unfortunately, I don't think that will work. Disabling NameMapper itself 
will.

This has been a long standing issue with NameMapper that, fortunately, 
people rarely experience as most library designers don't add `has_key` 
without also implementing the rest of the mapping/dict protocol.

The problem with checking for `keys` is the same as checking for 
`has_key`:  someone will have classes that aren't dicts but have `keys`. 
Maybe we could test for both or some other combination that is likely to 
have less false positives.

On Sat, 14 Aug 2010, R. Tyler Ballance wrote:

>
> 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
> --------------------------------------
>  GitHub: http://github.com/rtyler
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>

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