Detect rotation of subviews

Question

I have a view containing several subviews. I can detect and let the user rotate just one subview or the containing view using UIRotationGestureRecognizer. But I would like to be able to rotate any square collection of subviews, like so:

Initial state:

Rotating upper right square counter-clockwise

To get here

How can I achieve this behavior? How should I nest my view hierarchy?

Any pointers are appreciated :)

Answer 1

here's what I would do (pseudocode):

when rotation recognized:
    create new_layer
    new_layer.bounds = union_rect( frames of tiles to be rotated )
    new_layer addSublayers:(tiles to be rotated)

while rotation in progress:
    new_layer.transform = CATransform3DMakeRotation( angle, 0, 0, 1 )

when rotation complete:
    (original view).layer addSublayers:(tiles to be rotated)
    (tiles to be rotated) rearrange after rotation