willTransitionToTraitCollection not get called, why?

Question

I am trying to replace didRotateFromInterfaceOrientation with willTransitionToTraitCollection - in a UIViewController subclass - as doc says, but method is not get called when I am rotating device. Why?

Answer 1

If you're testing this on iPad it has regular trait collections for vertical and horizontal class for both orientations, thus it will not call this method when orientation changed.