On Oct 30, 2008, at 4:46 PM, Chuck Hill wrote:
Hi David,
On Oct 30, 2008, at 2:44 AM, David Avendasora wrote:
I have several places in my application where a large number of EOs
exist in the DB that are directly dependent upon other EOs. If the
depended-upon EOs change, then all the dependent EOs may need to be
updated.
Are these all guaranteed to be in memory at the same time? Do you
run multiple application instances?
Well... Multiple Apps (JC & Web) accessing the same DB via a common
foundation framework. But only one instance of each application.
This seems to me like the perfect use of the Observer Pattern.
Or not. It sounds more like Publish - Subscribe. Or is that the
same...?
Yep. Same thing.
For example. If a Part's BOM is updated the nutrition information
for that Part may need to be updated as well. Calculating the
current nutrition information is too expensive to do it everywhere
it is needed so it is saved in the database. I also maintain
historical nutritional information as well and that shouldn't be
updated, only the current information should be.
What I'd like to do is to have the "current" Nutrition object
observe the Part object.
Or have the part broadcast a NSNotification when it is modified.
Then any other objects can choose to subscribe to this notification
if they deem it interesting.
This sounds exactly like what I want. I figured there had to be a WO-
way of doing this.
If the Part object is updated in a significant way, then the
Nutrition object will get notified to update itself.
Publish - Subscribe gives a bit more decoupling between the change
and the response.
I guess the key is that the Part will not know what is significant to
the subscribers. Some subscribers could potentially ignore some
notifications. Is this possible?
What I'm trying to figure out is how to persist this information. I
don't think I want to model the relationship, do I?
I don't know. It is your model. What is it you are thinking of
persisting?
What subscribers a publishing object has and vise-versa. This isn't a
per-ec thing, it should be remembered across sessions.
I looked at EOObserving but I think that's more about catching
changes between two objects already in memory.
How would I model EOEnterpriseObject <<->> EOEnterpriseObject
anyway? Using EOIDs?
Now, I think I am lost.
Never-mind that last part. It was me trying to do things the hard way.
Dave
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to [EMAIL PROTECTED]
