Re: Quick question... NSNotificationCenter?
Re: Quick question... NSNotificationCenter?
- Subject: Re: Quick question... NSNotificationCenter?
- From: Chuck Hill <email@hidden>
- Date: Tue, 31 Aug 2004 17:11:39 -0700
On Aug 31, 2004, at 4:34 PM, Jake MacMullin wrote:
Is this one possible solution to the problem where you have multiple
instances of an application, and you want *all* instances to know *as
soon
as* one instance has written to the DB? Or is it meant for something
else?
No, this is not intended nor suitable for synchronization across
instances. This is intended to keep all the data within one instance
in synch. Hmmm, perhaps that should be within one EOF stack in synch.
Off hand I don't recall if it works across EOF stacks in the same
instance.
I know project Wonder has something for this - and others have
mentioned
having on instance (the writer) call web services on each of the other
instances as a means of letting them know about important changes.
That is the ChangeNotificationFramework. When you need it, you need
it, but often there are workable alternatives.
What methods have people found to the most effective/straight-forward?
Is
this something that a lot of people worry about - or are most people
happy
for some of the instances to have stale data?
It really depends on the specific situation: what data is getting
edited, how frequent the edits are, who needs to see the edits, how
stale of data is acceptable, how many optimistic locking failures can
be tolerated, etc. If you look on www.wodev.com you will see a number
of postings on getting fresh data. That, and careful consideration of
your requirements is the place to start. Fresh data is not free, it
has a cost (in terms of app speed, developer time, DB access etc).
Chuck
Regards,
Jake
On 1/9/04 1:22 AM, "Chuck Hill" <email@hidden> wrote:
There is usually only one instance per application. I'm not sure how
this works with JC.
Chuck
On Aug 31, 2004, at 1:13 AM, Rams wrote:
Sorry to be a bother with what seems like such a basic question, but
I
can't seem to find a clear answer anywhere in the docs... or what
looks
like a clear answer seems rather improbable. Is there only one
instance of NSNotificationCenter per web application? The docs seem
to
say so. If that is the case, then using NSNC on a 3-tier Java Client
app means that observers on every client receive all those little
notifications made by every object on every other client, no? Is
that
really the case, or are there multiple instances of NSNC, one per
client, or one per session, or one per something else?
--
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