Xcode 8 Swift 3: Modal presentation transitioning delegate not called

Question

Issue

The delegate functions within 'DrinkTransitioningDelegate' are not called. The 'td' instance remains in memory during and beyond the lifecycle of the presentation.

class PresentingViewController: UIViewController {

    let td = DrinkTransitioningDelegate()

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let item = inventory.beverages[indexPath.row]
        item.isSelected = true
        let controller = DrinkViewController(item: item)
        controller.delegate = self
        controller.transitioningDelegate = td
        controller.modalPresentationStyle = .custom
        //let navCon = UINavigationController(rootViewController: controller)
        //navCon.transitioningDelegate = td
        //navCon.modalPresentationStyle = .custom
        present(controller, animated: true)
    }

}

class DrinkTransitioningDelegate: NSObject, UIViewControllerTransitioningDelegate {

    func presentationControllerForPresentedViewController(presented: UIViewController, presentingViewController presenting: UIViewController!, sourceViewController source: UIViewController) -> UIPresentationController? {
        return DrinkPresentationViewController(presentedViewController:presented, presenting: presenting)
    }

    let animationController = DrinkAnimatedTransition()

    func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        animationController.isPresentation = true
        return animationController
    }

    func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        animationController.isPresentation = false
        return animationController
    }

    deinit {
        print("adf")
    }

}

History

• The question was raised for iOS 7 here
• The question was raised for iOS 9 here

Slough

Answer 1

Solution

Optional protocol functions are now a thing.

The delegate is comprised completely of optional functions, so there were no warnings.

These functions appeared to the compiler as my own custom functions.

func presentationControllerForPresentedViewController(presented: UIViewController, presentingViewController presenting: UIViewController!, sourceViewController source: UIViewController) -> UIPresentationController? {
    return DrinkPresentationViewController(presentedViewController:presented, presenting: presenting)
}

let animationController = DrinkAnimatedTransition()

func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    animationController.isPresentation = true
    return animationController
}

func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    animationController.isPresentation = false
    return animationController
}

These are the correct functions.

func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
    return DrinkPresentationViewController(presentedViewController:presented, presenting: presenting)
}

func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    let animationController = DrinkAnimatedTransition()
    animationController.isPresentation = true
    return animationController
}

func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    let animationController = DrinkAnimatedTransition()
    animationController.isPresentation = false
    return animationController
}

Slough

I've been stumped on a similar problem for hours... In my case, the two "animationController" functions get called, but not the "presentationController" function. The modalPresentationStyle is .custom. Help! This is driving me completely insane! ;-) – Zweig

Okay, figured it out... There's actually another version of public func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? that I copied from some example code. Can't recall the exact wording, but the compiler didn't recognize the error. – Zweig

Answer 2

Your transitioningDelegate = self may not be called early enough. The solution around my issue was to add the following, then both animationController(forPresented..) and animationController(forDismissed..) we're called.

init() {
    super.init(nibName: nil, bundle: nil)
    modalPresentationStyle = .overCurrentContext
    transitioningDelegate = self
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    modalPresentationStyle = .overCurrentContext
    transitioningDelegate = self

}

You may not need the following line, but left in here in many cases if you have a partial half drawer screen.

modalPresentationStyle = .overCurrentContext

Unfamiliar

Adding the transitionDelegate to the inits fixed my issue, but I used .custom for the presentation style in order for the presentationController(..) method to work. – Pinto