[Zope-dev] Overriding __getattr__ for requests only.

[Jim Fulton]

"Jeff K. Hoffman" wrote:
> 
> Hello, everyone.
> 
> I am trying to write a new subclass of OFS.Folder (as a python product) to
> do the following: When a user requests /myFolder/index_html, myFolder
> will search itself, then its list of 'parents', returning the attribute
> from one of them if they have it, and raising an AttributeError if not.
> 
> I have had some moderate success by overloading __getattr__ as follows:
> 
>   def __getattr__(self, name):
>       try:
>           return OFS.Folder.Folder.__getattr__(self, name)
>       except:
>           for parent in self.parentList:
>               try:
>                   return getattr(parent, name)
>               except AttributeError:
>                   pass
>           raise AttributeError, name

Never override __getattr__ on persistent objects.  __getattr__ is
already overridden by the persistence machinery and overriding it 
yourself will cause big problems.

You can accomplish the same thing by overriding __getitem__, being careful
to include (or call) the base __getitem__ inherited from ObjectManager.

When publishing a URL, Zope tries __bobo_traverse__, then __getattr__, 
then __getitem__.

If you *don't* want to acquire, you will also need to mix-in 
Acquisition.Explicit, before Folder (or ObjectManager).

(snip)

Jim

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