Understanding crashlytics UIKit errors

Question

I am having trouble understanding the UIKit crash reports that I am receiving:

Is there a way of finding out what line of code caused this:

Crashed: com.apple.main-thread
0  UIKit                          0x195694264 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 444
1  UIKit                          0x1955d0950 _runAfterCACommitDeferredBlocks + 292
2  UIKit                          0x1955c29ec _cleanUpAfterCAFlushAndRunDeferredBlocks + 528
3  UIKit                          0x195336648 _afterCACommitHandler + 132
4  CoreFoundation                 0x18f1c09a8 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
5  CoreFoundation                 0x18f1be630 __CFRunLoopDoObservers + 372
6  CoreFoundation                 0x18f1bea7c __CFRunLoopRun + 956
7  CoreFoundation                 0x18f0eeda4 CFRunLoopRunSpecific + 424
8  GraphicsServices               0x190b58074 GSEventRunModal + 100
9  UIKit                          0x1953a9058 UIApplicationMain + 208
10 FlexConnect                    0x1001b48c8 main (AppDelegate.swift:20)
11 libdyld.dylib                  0x18e0fd59c start + 4

The error itself is:

Crashed: com.apple.main-thread

EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000010

EDIT:

Based of the answer below, I'm wondering if it is advisable to use:

func topMostController() -> UIViewController {
    var topController: UIViewController = UIApplication.sharedApplication().keyWindow!.rootViewController!
    while (topController.presentedViewController != nil) {
        topController = topController.presentedViewController!
    }
    return topController
}

and always call

let topVC = topMostController().dismiss(animated: true, completion: nil)

everywhere in my app where I currently have self.dismiss(animated: true, completion: nil)?

Is this a necessary check or how can I pin down where self.dismiss is having an issue?

Some sample dismissals:

@IBAction func returnToDash(_ sender: UIButton) {
     self.dismiss(animated: true, completion: nil)
}

let pending = UIAlertController(title: "\n\n\n\(title)", message: nil, preferredStyle: .alert)
displayActivityAlertWithCompletion2(ViewController: self, pending: pending){_ in
   Helper_StatusCheck.doSync(_cleanSync: false){
        Prefs.is_Syncing = false
        DispatchQueue.main.async {
            pending.dismiss(animated: true){
                   Toast(text: "Upload sync completed").show()
                   self.dismiss(animated: true, completion: nil)
            }
        }
   }
}

where displayActivityAlertWithCompletion2 looks like:

public func displayActivityAlertWithCompletion2(ViewController: UIViewController, pending: UIAlertController, completionHandler: @escaping ()->())
{
    //let pending = UIAlertController(title: "\n\n\n"+title, message: nil, preferredStyle: .alert)
    //create an activity indicator
    let indicator = UIActivityIndicatorView(frame: pending.view.bounds)
    indicator.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    indicator.color = UIColor(rgba: Palette.loadingColour)
    //add the activity indicator as a subview of the alert controller's view
    pending.view.addSubview(indicator)
    indicator.isUserInteractionEnabled = false
    // required otherwise if there buttons in the UIAlertController you will not be able to press them
    indicator.startAnimating()



    ViewController.present(pending, animated: true, completion: completionHandler)
}

EDIT 2 :

Some sample popover methods in my app:

 @IBAction func search(_ sender: UIButton) {
        if let popView = UIStoryboard(name: "AssetCommon", bundle: nil).instantiateViewController(withIdentifier: "searchPop") as? searchPopVC {
            popView.delegate = self
            popView.modalPresentationStyle = .popover;
            popView.popoverPresentationController?.delegate = self
            popView.popoverPresentationController?.barButtonItem = searchButton
            popView.popoverPresentationController?.permittedArrowDirections = .any
            popView.preferredContentSize = CGSize(width: 300, height: 70)
            self.present(popView, animated: true, completion: nil)
        }
    }

and search pop:

class searchPopVC: UIViewController
{
    @IBOutlet weak var searchBar: UISearchBar!

    weak var delegate: SearchPopDelegate?

    override func viewDidLoad()
    {
        super.viewDidLoad()

        searchBar.delegate = self;
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
    }

    @IBAction func performSearch(_ sender: UIButton)
    {
        let term = searchBar.text ?? "";
        delegate?.performSearch(with: term)
        self.dismiss(animated: true, completion: nil);
    }
}

extension searchPopVC: UISearchBarDelegate
{
    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
        let term = searchBar.text ?? "";
        delegate?.performSearch(with: term);
        self.dismiss(animated: true, completion: nil)
    }
}

Answer 1

You won't be able to find the line of code from this crash. However, this crash happens when the view controller you use to call dismiss(animated:completion:) is removed from the view hierarchy prior to the animation completing.

Depending on how your code is setup, you can try to request a view controller higher up to call the dismissal. Another solution could be to retain the view controller in a property until your for sure done with it.

Edit: 1/5/18

In response to the comments, here is an example of how a function can be made for view controllers that logs an event and dismisses.

extension UIViewController {
    func dismissAndLog(animated: Bool, completion: (() -> ())? = nil) {
        // Here are two examples of how your view controller can be identified.
//        let id = title
        let id = String(describing: type(of: self))
        CLSLogv("Dismissed View Controller: %@", getVaList([id]))

        dismiss(animated: animated, completion: completion)
    }
}

I'm not entirely familiar with Crashlytics or their API, so if this logging is giving you issues, you can check out these links.

• https://docs.fabric.io/apple/crashlytics/enhanced-reports.html#custom-logging-in-swift
• How to use Crashlytics logging in Swift?

Also I don't know how they provide the data to you, so I can't explain to you the best way to parse it. However certainly the timestamps can be successfully used as a final solution. You can also try emailing their support asking for the best way to map these logs to the crash.