[Zope3-Users] Trouble understanding events, handlers, subscribers (Trying to use component architecture outside of Zope)

[Dominik Huber]

Jeff Shell wrote:

>I'm writing a small command line tool that uses parts of Zope 3's
>component architecture (zope.component, zope.interface, zope.schema),
>and just includes those packages and a couple of supporting ones found
>in dependencies (zope.i18nmessageid, exceptions, texting). No
>zope.app, publisher, server, etc. And (at present) no C code, so no
>zope.hookable either. And no ZCML.
>
>I'd like to use events in my tool, but I'm confused. I'm having a hard
>time understanding the terminology in zope.component / zope.interface
>regarding Subscribers and Handlers. I don't know if those are wired to
>zope.event.notify at all.
>  
>
Nope, you have to register a dispatcher first that invokes the 
subscribers registered within the adapter-registry.
See zope.app.event.dispatching

>I don't know how to translate something like:
>
><subscriber for="myapp.interfaces.IBeforeInstallEvent"
>    handler="myapp.foo.ensurePaths"/>
>
>into zope.component.provide... provideHandler? provideSubscriber?
>  
>
from zope.component import getGlobalSiteManager

gsm = getGlobalSiteManager()
gsm.subscribe(required, provided, factory)

the zcml example above:
gsm.subscribe((IBeforeInstallEvent,), None, ensurePaths)

>I think I'm just not understanding the relationship of 'for' (in the
>ZCML) to the provideHandler / provideSubscriber concepts of 'adapts'
>and 'provides', and what that means for me looking to subscribe to an
>event with a plain old function. Or class. Or instance.
>  
>
A callable that takes one or more arguments corresponding to the number 
of required interfaces.

Regards,
Dominik