Re: Listening for changes on an EO
Re: Listening for changes on an EO
- Subject: Re: Listening for changes on an EO
- From: Chuck Hill <email@hidden>
- Date: Thu, 9 Jul 2009 13:51:25 -0700
On Jul 9, 2009, at 1:28 PM, Lon Varscsak wrote:
Uh, another question. :) Since I have a custom EO super-super class,
I decided to try to implement this in takeStoredValueForKey(..).
It works, although I was also trying to post the "old" value, and
asking for this current value at this point makes EOF not so
happy...but that's not strictly required for my needs.
However, it does post notifications even for fetched objects, what
would be the best way to only post changes after fetching?
This might be closer to what you want:
http://developer.apple.com/documentation/InternetWeb/Reference/WO542Reference/com/webobjects/eocontrol/EOObserverCenter.html
That would give you the "before" picture. You can set a flag there
too (or in willChange()). If the flag is set, then in
takeStoredValueForKey, you can send out the after notification and
clear the flag. willChange() will not get called for fetched objects.
Chuck
On Thu, Jul 9, 2009 at 12:43 PM, Lon
Varscsak<email@hidden> wrote:
Thanks for the tips!
-Lon
On Thu, Jul 9, 2009 at 12:34 PM, Chuck Hill<chill@global-
village.net> wrote:
On Jul 9, 2009, at 12:26 PM, Lon Varscsak wrote:
Thanks. I figured there was nothing built to do exactly what I
needed, but I figured I would ask.
Do you know if there is much overhead if I implemented this in my
EO
superclass even if there were no observers?
EOF makes heavy use of notification. I would not expect there to
be much
overhead. You will probably want to qualify the notification with
the EC
(depending on what it is you are trying to do) to limit the number
of
observers. And then keep the method receiving the notification
fast. The
notifications are synchronous, so you don't want anything slow in
this
method.
Chuck
-Lon
On Thu, Jul 9, 2009 at 11:50 AM, Simon
McLean<email@hidden> wrote:
also, if you are using wonder, check out
hasKeyChangedFromCommittedSnapshot in ERXGenericRecord. maybe
listen
for the notification mentioned by chuck, then use
hasKeyChangedFromCommittedSnapshot to check the particular key
you are
looking at.
simon
2009/7/9 Chuck Hill <email@hidden>:
On Jul 9, 2009, at 10:24 AM, Lon Varscsak wrote:
Is there a way for a controller object to listen for changes
to an EO
(and a specific key)?
Thanks,
Lon
EOEditingContext has
ObjectsChangedInEditingContextNotification, but it
is
on an object by object basis, not a key by key one.
You could implement this in your EO super class.
Chuck
--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase
their overall
knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall
knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
_______________________________________________
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