[rt-users] Enforcing uniqueness on Custom Field values?

[Riggle, Kevin]

Hi all,

Is there a way to ensure that multiply-valued Custom Fields (eg. a "Enter
multiple values" CF) don't end up with duplicate entries?

What I'm trying to do more broadly:  I have another ticketing system I'm
integrating with, and a single RT ticket can be associated with multiple
tickets in this other system.  I've added its subject tag to
$ExtractSubjectTagMatch, but I also want to have an easy link to go visit
the other ticket.  I've created a CF with the right URL pattern, and I'm
using a patched version of RT::Extension::ExtractCustomFieldValues to pull
the subject tags into the CF, but if a new message comes in which adds a
new subject tag, the earlier subject tags get added again.

I can further hack RT::Extension::ExtractCustomFieldValues to ensure
uniqueness on insertion, but this seems like something which might be
better enforced at the CF level ("Enter multiple unique values").  Is
there a way to do that?  Or, is there a better way to solve my larger
problem of links to the other ticketing system?

- Kevin