[Zope3-dev] Heads up: Adapter registry api restructuring

[Jim Fulton]

The API adapter registry, used by the adapter and other services is
going through some restructuring. This will mainly affect the adapter
service and those other few bits of application that use this registry.

This registry was recently known as the surrogate registry. I never defined
an interface for this thing. Here's one that I plan to change the implementation
to conform to:


class IAdapterRegistry(Interface):
     """Provide an interface-based registry for adapters

     This registry registers objects that are in some sense "from" a
     sequence of specification to an interface and a name.

     No specific semantics are assumed for the registered objects,
     however, the most common application will be to register factories
     that adapt objects providing required specifications to a provided
     interface.

     """

     def register(required, provided, name, value):
         """Register a value

         A value is registered for a *sequence* of required specifications, a
         provided interface, and a name.
         """

     def lookup(required, provided, name, default=None):
         """Lookup a value

         A value is looked up based on a *sequence* of required
         specifications, a provided interface, and a name.
         """

     def subscribe(required, provided, name, subscriber):
         """Register a subscriber

         A subscriber is registered for a *sequence* of required
         specifications, a provided interface, and a name.

         Multiple subscribers may be registered for the same (or
         equivalent) interfaces.
         """

     def subscribers(required, provided, name):
         """Get a sequence of subscribers

         Subscribers for a *sequence* of required interfaces, a provided
         interface, and a name are returned.
         """

This change represents a shift of some responsibilities out of
the registry.  In particular:

- In the special case of a single object being adapter, the registry
   does not consider whether the object provides the desired interface.
   This is already the case for the adapter register.

- The registry no longer tries to call the registered values. In other
   words, there is no special factory interpretation given to the registered
   objects. That's the job of the service using the registry.

Note that the required argument can be an empty tuple.  Yes, this
unifies adapters and utilities at the registry level. :)

This probably spells the end of the utility service, but *not* the end
of getUtility and queryUtility. These functions will simply use the adapter
service.

Jim

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