Am Dienstag, 19. Dezember 2006 08:17 schrieb Christian Theune:
> Hi,
> Florian Lindner wrote:
> > Hello,
> > I have the following situation:
> >
> > An object represents an RSS feed. It should be updated like every 20
> > minutes. If there is something new a Jabber message should be send out.
> >
> > Currently I have it implemented with an scheduler loop that emits an
> > refreshRSSFeed event evey 20 minutes. My problem is that a handler for an
> > event must be a static function, but I want a handler function to be
> > called as a member of every instantiated RSS feed object.
> >
> > Another idea I have:
> > Implement an utility where the RSS feeds could register a function that
> > is called every 20 minutes.
> > Another way would be that this utility takes an URL and monitors the URL
> > for changes and only notifies the RSS Feed object in case of a change.
> >
> > How would you do that?
> So there's two problems here: scheduling and notifying persistent
> objects about an event.

No, only the notifying problem.

> I don't have a good idea about the scheduling right now, except the hint
> that using a 'zopectl run' script might be worthwhile.  I'm not sure
> what a 'scheduler function is'.

I use the scheduler package from the Zope3 trunk and so far it works for me.

> About notifying persistent objects: There is a method
> 'getAllUtilitiesRegisteredFor(interface)' which might help you. Have a
> look at zope/app/catalog/ beginning from line 150
> (indexDocSubscriber) how the catalog handles events and dispatches them
> to multiple catalogs. I think this pretty much matches your use case if
> you make each RSS feed a (named) utility.

The RSS feed is a object that users could add and remove to arbitrary 
(sub-folders of there home-dir) folders. I would rather regard it as content 
object and I don't like adding utilities to content space (I have never 
really understood why content- and software-space have been mixed up).
It would be possible, I think even technically superior to the next solution 
but somehome I don't like.

> Of course you could also have a utility that maintains references to all
> RSS feed objects and simply loops over them and calls a method for
> refreshing.

That's something I had mentioned in my posting too. It has advantage that the 
feeds could decide if they want to be called or not, whereas by 
the "utility-way" they would always be called.

Thanks for your input,

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