Trac - How Do I Access Custom Ticket Fields In Iticketchangelistener?

I'm trying to write my own Trac plugin to notify an external system of changes to tickets matching a certain criteria. From my research so far, I've figured out that implementing

Solution 1:

The sources are wrong about custom ticket fields. The value-by-name approach should work. And *old_values* contains all fields values, including custom fields too. That's it.

You may want to look at the TracAnnouncer source for some change-listener coding examples.