An approach I like to take in these situations is to have another
application that is responsible for user creation. Both apps would
message this UserManager WOApp (via web services is one way) and it
would either return a global ID or an error. The app would keep a
running list of all users so that duplication is not possible.
On Nov 15, 2005, at 6:14 AM, Miguel Arroz wrote:
Hi!
I was wondering how to do something like this... imagine a form
to create a new user on a site. The code would be something like:
EOFetchSpecification fetchSpecificationForUserWithLoginArroz =
blah blah blah; // line 1
NSArray objects = someContext.objectsWithFetchSpecification
(fetchSpecificationForUserWithLoginArroz); // line 2
if( objects.count() == 0 ) { // line 3
/* create user with login arroz */
}
The problem is... what happens if two or more instances of the
application run this code at the same time? Specifically, if two
instances run both line one and line two at the exactly same time,
when running line 3, one of them will create a second user with the
same login.
Of course, one way of avoiding this is to make the login the
primary key... but I don't like this method at all. The other way I
see is using table locking. How to do that in WebObjects? I assume
it's not easy, as I shouldn't even know there is something called
"table" at this level...
How do you take care os this problem on your apps?
Yours
Miguel Arroz
"I felt like putting a bullet between
the eyes of every Panda that wouldn't
scr*w to save its species." -- Fight Club
Miguel Arroz
http://www.ipragma.com
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