transitioningDelegate never called after Segue transition - swift3

Question

So I'm trying to implement a custom animation as my app transitions from one View Controller to another, but for some reason the animateTransition function in my custom animation class is never called.
For the record, I'm using Xcode 8 and writing in Swift 3. The problem I'm trying to over come, is that the function is never called - I'll sort out the actual animation in the future, for now its
Here is the code in my CustomPresentAnimationController class, which should handle the transition animation...
import UIKit
class CustomPresentAnimationController: NSObject, UIViewControllerAnimatedTransitioning, UIViewControllerTransitioningDelegate, UINavigationControllerDelegate {
let duration = 0.5
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
print("Checking duration")
return duration
}
func animationController(forPresented presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
print("This ran 1")
return self
}
func presentationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
print("This ran 2")
return self
}
func animationController(navigationController: UINavigationController, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
print("This ran 3")
return self
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
print("It's working!")
guard let fromView = transitionContext.view(forKey: UITransitionContextViewKey.from) else {
return
}
guard let toView = transitionContext.view(forKey: UITransitionContextViewKey.to) else {
return
}
let container = transitionContext.containerView
let screenOffDown = CGAffineTransform(translationX: 0, y: -container.frame.height)
let screenOffUp = CGAffineTransform(translationX: 0, y: container.frame.height)
container.addSubview(fromView)
container.addSubview(toView)
toView.transform = screenOffUp
UIView.animate(withDuration: duration, delay: 0.0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0.8, options: [], animations: {
fromView.transform = screenOffDown
fromView.alpha = 0.5
toView.transform = CGAffineTransform.identity
toView.alpha = 1
}) { (success) in
transitionContext.completeTransition(success)
}
}
}
Here is the code for my ViewController (which both of my View Controllers reference)...
import UIKit
class ViewController: UIViewController, UINavigationControllerDelegate, UIViewControllerTransitioningDelegate {
override func viewDidLoad() {
if transitioningDelegate != nil {
print("Should do something...")
print(transitioningDelegate)
} else {
print("Transitioing Delegate set to nil")
}
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.navigationController?.delegate = self
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
let customPresentAnimationController = CustomPresentAnimationController()
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
print("doing our custom transition")
print(segue.destination)
let destination = segue.destination
destination.transitioningDelegate = customPresentAnimationController
}
}
When I run the code, and click on the button I provided, which links to my seance View Controller, and is set to 'Present Modally', the view changes with the standard transition (slides up from the bottom) - and the following is printed out to Xcode:
Transitioing Delegate set to nil
doing our custom transition
<moduleView.ViewController: 0x7fe427f09a40>
Should do something...
Optional(<moduleView.CustomPresentAnimationController: 0x60800002e980>)
Obviously the first line is just as the first view loads, all the rest shows that my transitionDelegate is set on the Segue destination, and is indeed loaded in as the second view loads, and that the transitionDelegate is set to CustomPresentAnimationController... yet none of the functions in that class are ever called as it never prints anything out from those functions.
Any help appreciated!

Answer 1

Ensure the method signature for implementing the delegate matches the updated Swift 3 syntax.