Cocoa interface element to add/remove fields like rules editor in Mail.app

Question

What is the name of the Cocoa interface with buttons to add/remove rows?

Here is a picture of it in the mail app

Is this a standard interface or is it a custom feature?

Answer 1

The class you're looking for is NSRuleEditor. If you want something specialized for editing NSPredicate objects, take a look at the NSPredicateEditor subclass.