[Zope] Change Notification

[Bob Barter]

Is there a way for an object to be notified that it has been modified?

In particular, I want to create Relation objects that relate two arbitrary
Folders.  Creating the Relation object with a ZClass is easy (even for a newbie
like me :-) ), but I need to update the relation links if the destination folder
is moved.

My thinking is that I need a parentChanged method that is invoked by a parent.
parentChanged would then recursively invoke parentChanged for each of its child
folders.  The purpose of parentChanged would be to look for any relation objects
that referenced the old location and either 1) change the reference to the new
location if the old location is no longer valid (i.e. a Cut/Paste operation), or
2) add the new location if the old location is still valid (i.e. a Copy/Paste
operation).

This sounds expensive, and I'm not sure how to kick off the process.  Does a
"Paste" create a new instance?

Thanks for the help,
Bob Barter


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Re: [Zope] Change Notification

[Tino Wildenhain]

Hi,

Bob Barter wrote:
> 
> Is there a way for an object to be notified that it has been modified?
> 
> In particular, I want to create Relation objects that relate two arbitrary
> Folders.  Creating the Relation object with a ZClass is easy (even for a newbie
> like me :-) ), but I need to update the relation links if the destination folder
> is moved.

if it is in aqisition path,   may help. It would
give
you the URL of the object whereever it is at the moment.
May be, you could use ZCatalog otherwise.

HTH
Tino Wildenhain

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Re: [Zope] Change Notification

[Itamar Shtull-Trauring]

Bob Barter wrote:
> 
> Is there a way for an object to be notified that it has been modified?

Use ZPatterns 0.4, it allows you to be notified of events - change, add and
delete of objects.

-- 
Itamar S.T.  [EMAIL PROTECTED]
Fingerprint = D365 7BE8 B81E 2B18 6534  025E D0E7 92DB E441 411C

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Re: [Zope] Change Notification

[Tres Seaver]

Itamar Shtull-Trauring <[EMAIL PROTECTED]> wrote:
> 
> Bob Barter wrote:
> > 
> > Is there a way for an object to be notified that it has been
> > modified?
> 
> Use ZPatterns 0.4, it allows you to be notified of events - change,
> add and delete of objects.

I may be confused, but normally the object should _know_ that it has
been modified, because one of its methods has been called.  In fact,
the usual pattern for this is to have the object notify other
interested parties ("Observers") of the fact that it has changed.

2.2 has experimental support for this -- see
$ZOPE/lib/python/OFS/DefaultObservable.py.  Also, see the writeup
on this in the Intefaces wiki (start from
http://www.zope.org/WikiCentral -- look for ObserverAndNotification.

Tres.

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