RFC: schema by interface

Finally, insomnia gave me enough time to try this:

http://svn.plone.org/svn/archetypes/Archetypes/branches/whitmo-schema-by-iface/

there is one test failure and one error(not sure if these are related). 
      Essentially, all calls to BaseObject.Schema now get passed to 
ISchema(self).  The adapter takes care of fetching the schema object 
from the instance and doing the aquisition wrapping.

all but 2 of the tests pass. haven't tried much else.

The adapter acts as a proxy of sorts, delegating all calls to the 
wrapped schema object (this is actually achieved by fully copy the 
schemas __dict__ and __class__ over the adapter's).  This is a bit of 
hack, but it should give some ideas about other possibilities in this 
realm.

here is one simpler alternative, registering a function as the schema 
factory requires less code and is probably easier to understand::


 >>> from Acquisition import ImplicitAcquisitionWrapper as wrap
 >>> def pschema_fetcher(inst):
...     return wrap(inst.schema)

I'm curious to see if the following would work::

 >>>from mytype import MyATSchema # some schema built at import time
 >>>def module_schema_fetcher(inst):
...    return wrap(MyATSchema)

The next obvious step is something like this::

 >>> from archetypes.schema.interface import ILocalSchema
 >>> from zope.component import getUtility
 >>> def utility_schema_fetcher(inst):
...     util = getUtility(ILocalSchema, name="schema_locker")
...     schema=util.composeSchema(inst)
...     return wrap(schema)


Anyhoo, framework-headz have a look, give me some feedback.

-w



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