Re: RFC: schema by interface

whit wrote:
> Finally, insomnia gave me enough time to try this:
> 
> http://svn.plone.org/svn/archetypes/Archetypes/branches/whitmo-schema-by-iface/

i've been (inadvertently) not following this list for a few months now 
(forgot to subscribe when i switched to a new NNTP reader), am just now 
getting caught up... i replied to an earlier inquiry from optilude 
earlier today, missed this thread altogether... sorry about that.

> 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.

as i mentioned in the earlier post, i'd recommend using ISchemaConsumer 
as a marker interface on the content and ISchemaProvider as the 
interface that actually provides the schema, just to make things a bit 
more clear.

> 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.

hmm.... yeah... not sure about this.

> 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.

i'd definitely lean towards these options... it feels safer and cleaner 
to me to return a schema object that is wrapped only in the context 
object, not the view itself.

-r



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