> my current proposal regarding the association of objects to sessions,
> as well as the optional association of objects and classes to
> "session contexts", is as follows:
(...)
That's very nice! I'm looking forward to refactor our application
to use this interface.
> # returns the session assocaited with the current "session context".
> # the "session context" may be specific to a particular class or
> object
> def current_session(instance=None, klass=None):
> # objects/classes may implement the __sessioncontext__
> method which returns a
> # sessioncontext callable
> if instance is not None and hasattr(instance,
> '__sessioncontext__'):
> context = instance.__sessioncontext__()
> return context()
> elif klass is not None and hasattr(klass,
> '__sessioncontext__'):
> context = klass.__sessioncontext__()
> return context()
I suggest a change here. The __sessioncontext__ method for a class
becomes the __sessioncontext__ method for the instance once it's
created. I suggest turning it into something like:
def current_session(object=None):
if object:
context = getattr(object, "__instancecontext__", None)
if (context and
getattr(context, "im_self", True) is not None):
session = context()
if session:
return session
context = getattr(object, "__classcontext__", None)
if context:
session = context()
if session:
return session
context = default_session_context(object)
if context:
session = context()
if session:
return None
return None
This implementation provides the following features:
- Allows separate logic for instances and classes.
- Allows a given type to implement only the class context, and
have it working for instances as well (classmethods).
- Allows a given type to implement *both* of them, and call
each one when appropriate.
- Allows a given type to implement both of them, but decide to
optionally fallback to the more general context at runtime
(returning None).
> # allows a default "session context" function to be plugged in
> # at the module level. the threadlocal mod plugs in one particular
> implementation
> # of this function.
> def _default_session_context(instance=None, klass=None):
> return None
It'd be nice to implement a supported way to overload both of
these functions. Doing thirdparty.some_func = my_func always
seems like an unsupported hack that will break in the next
upgrade.
> def object_session(instance):
> hashkey = getattr(instance, '_sa_session_id', None)
> if hashkey is not None:
> return _sessions.get(hashkey)
> else:
> return None
That could potentially be merged at the top of the method above.
It also sounds like the method names are reversed, but that's
minor.
--
Gustavo Niemeyer
http://niemeyer.net
-------------------------------------------------------
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