Conditional required field in CFormModel

Let's say I've following simple CFormModel

I want to make calcRanking required field when manual is not set and manualRanking required when calcRanking is not set. In shortcut, one of this field should be filled when posting form. I think I can do this by creating my own validation rule. Is there any other way to do this, e.g. may I use bizrules for that?

Which approach is better, more convenient?

how about a "scenario" option in the rules()?

Isn’t scenario more suitable for different actions? I want to have one of this field filled in one action (both are displayed in the view). I’ll try to play a little bit with scenarios and see whats happened :)

I don’t think there is that option. i was suggesting you create a new class that adds it. :)