Completion block for popViewController

Question

When dismissing a modal view controller using dismissViewController, there is the option to provide a completion block. Is there a similar equivalent for

Answer 1

2020 Swift 5.1 way

This solution guarantee that completion is executed after popViewController is fully finished. You can test it by doing another operation on the NavigationController in completion: In all other solutions above the UINavigationController is still busy with popViewController operation and does not respond.

public class NavigationController: UINavigationController, UINavigationControllerDelegate
{
    private var completion: (() -> Void)?

    override init(rootViewController: UIViewController) {
        super.init(rootViewController: rootViewController)
        delegate = self
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    public override func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool)
    {
        if self.completion != nil {
            DispatchQueue.main.async(execute: {
                self.completion?()
                self.completion = nil
            })
        }
    }

    func popViewController(animated: Bool, completion: @escaping () -> Void) -> UIViewController?
    {
        self.completion = completion
        return super.popViewController(animated: animated)
    }
}