At 04:42 PM 6/25/2007 -0500, Ian Bicking wrote:
>Phillip J. Eby wrote:
>>At 02:28 PM 6/25/2007 -0500, Ian Bicking wrote:
>>>Potentially a Zope-style minimal event framework would
>>>work. Maybe something like:
>>>
>>> send_signal(signal_name, signal_data)
>>> subscribe(signal_name, listener)
>>That was what I was wondering, too, except I was thinking it would
>>be sufficient to use entry points for subscription, but only invoke
>>the entry points whose modules are in sys.modules. In other words,
>>never actually import a module in order to invoke a callback. That
>>way, subscription is a natural side effect of importing the modules
>>that contain the listeners. Something like:
>>def send_signal(group, name, *args, **kw):
>> for ep in iter_entry_points(group, name):
>> if ep.module_name in sys.modules:
>> ep.load()(*args, **kw)
>
>I don't think that makes sense for this case. The way I imagine using it is:
>
>class MyApplication(object):
>
> def __init__(self, db):
> self.db = db
> subscribe('reload_resources', self.reload)
> def reload(self, data=None):
> self.db.close()
> self.db.open()
I guess I wasn't clear. The point is that the approach I'm
suggesting allows event subscribers to be decoupled. A library could
have an "on_reload" function, for example, that references a
library-specific event system. Some frameworks, after all, are going
to have their own event systems.
So a bridge from the bus to zope.event, for example, could just
create objects and notify() them, and frameworks that are okay with
depending on zope.event can use that.
>That is, I subscribe one particular thing when it is applicable, not
>because the library is on the system.
That's why the code I suggested only invokes entry points that are
*already imported* -- i.e., that someone is using.
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