Re: Enforcing uniqueness of data
Re: Enforcing uniqueness of data
- Subject: Re: Enforcing uniqueness of data
- From: Chuck Hill <email@hidden>
- Date: Wed, 7 Sep 2005 11:33:16 -0700
On Sep 7, 2005, at 10:00 AM, Daniel Eggert wrote:
I need the login of my user EO to be unique. Since the login is
something the user enters, it is not the PK.
How would I go about ensuring this? If I fetch from the database
and then write if it is unique, someone might be able to write to
the database in the meantime.
This post
<http://lists.apple.com/archives/webobjects-dev/2004/Jun/
msg00249.html>
suggests locking. Is it a sane approach? How would I do such a
thing with EOF?
I'd consider the other option that it mentions, adding a unique
constraint. You will then have to catch exceptions from save changes
and determine if the exception was a DB server side exception
(EOGeneralAdaptorException) and, if so, if the exception was raised
due to a violation of the unique constraint. Unfortunately, the
exceptions and errors returns from DB servers are vendor specific so
you will end up writing handling code for each server you need to
support.
You can do the locking too, and it is possible, but I can't whip the
EOF code off the top of my head.
Chuck
--
Practical WebObjects - a book for intermediate WebObjects developers
who want to increase their overall knowledge of WebObjects, or those
who are trying to solve specific application development problems.
http://www.global-village.net/products/practical_webobjects
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