UINavigationController Custom transition issue - ios

Question

I followed many tutorials about how to create custom transitions but most of them apply to the presentation and dismissing of the view controllers. I just want to apply custom transitions to the UINavigationController for the push/pop actions.
After reading apple documentation I created simple project to test if it works.
Here is all my code for custom Navigation Controller:
class CustomNC: UINavigationController {
override func viewDidLoad() {
super.viewDidLoad()
delegate = self
}
}
extension CustomNC: UINavigationControllerDelegate {
func navigationController(
navigationController: UINavigationController,
animationControllerForOperation operation: UINavigationControllerOperation,
fromViewController fromVC: UIViewController,
toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
print("Creating UIViewControllerAnimatedTransitioning for operation: \(operation.rawValue)")
return self
}
}
extension CustomNC: UIViewControllerAnimatedTransitioning {
func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
print("Returning duration for transition")
return 1.0
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
print("Animating transition")
let container = transitionContext.containerView()!
let fromView = transitionContext.viewForKey(UITransitionContextFromViewKey)!
let toView = transitionContext.viewForKey(UITransitionContextToViewKey)!
// set up from 2D transforms that we'll use in the animation
let offScreenRight = CGAffineTransformMakeTranslation(container.frame.width, 0)
let offScreenLeft = CGAffineTransformMakeTranslation(-container.frame.width, 0)
// start the toView to the right of the screen
toView.transform = offScreenRight
// add the both views to our view controller
container.addSubview(toView)
container.addSubview(fromView)
// get the duration of the animation
// DON'T just type '0.5s' -- the reason why won't make sense until the next post
// but for now it's important to just follow this approach
let duration = self.transitionDuration(transitionContext)
// perform the animation!
// for this example, just slid both fromView and toView to the left at the same time
// meaning fromView is pushed off the screen and toView slides into view
// we also use the block animation usingSpringWithDamping for a little bounce
UIView.animateWithDuration(
duration,
delay: 0.0,
usingSpringWithDamping: 0.5,
initialSpringVelocity: 0.8,
options: [],
animations: {
fromView.transform = offScreenLeft
toView.transform = CGAffineTransformIdentity
}, completion: { finished in
// tell our transitionContext object that we've finished animating
transitionContext.completeTransition(true)
})
}
}
Then I simply create two default view controllers First and Second. First has UIButton with show action to the Second. First is embedded in NavigationController and this NavigationController has Custom Class set to CustomNC.
After running I see V1 controller but when I tap UIButton application crash without any error message. In Logs I see only those lines:
Creating UIViewControllerAnimatedTransitioning for operation: 1
Returning duration for transition
(lldb)
So as I understand the delegate is visible and navigation controller is using this delegate properly. When transition starts it gets the animation duration time interval but animateTransition method is never called because I don't see "Animating transition" message in log.
Can somebody point me where I have problem?