UINavigationController push crash

Question

I have a NestedViewController which I am trying to push into a UINavigationController. This causes a crash with a following stack trace:

Additionally:

All of this is happening on the main thread
This reproduces both on iOS 11 and 12
animated flag doesn't change anything
NestedViewController gets modally presented somewhere else in the app and it does so successfully, without crashing
NestedViewController gets its layout from a storyboard
NestedViewController with its view initialized programmatically and identical to storyboards layout still causes a crash
Pushing an empty UIViewController doesn't cause a crash

What am I doing wrong?

UPD1: I made this yet this doesn't cause a crash:

let controlla = { () -> UIViewController in
    let cont = UIViewController()
    cont.view = {
        let view = UIView()

        view.backgroundColor = UIColor.green
        let stack = UIStackView(arrangedSubviews: [ {
            let view = UIView()
            view.backgroundColor = UIColor.yellow

            view.snp.makeConstraints { make in
                make.height.equalTo(128)
            }
            return view
        }() ])
        view.addSubview(stack)

        stack.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
        }

        return view
    }()
    return cont
}()

controller.pushViewController(controlla, animated: true)

UPD2: On the request of user Adeel in the comment here is what it says in the console upon an abort breakpoint hit:

libc++abi.dylib: terminating with uncaught exception of type NSException

If it was so simple and the message was there, this question wouldn't really exist, would it.

UPD3: So to extend my investigation I have uninstalled all of the views inside the view controller except for the root one.

The scene tree, while at it, started to look like this:

Then, of course, I got rid of all outlets and the code that was in the view controller.

It still crashes. The modal present still works fine though.

UPD4: I renamed the NestedViewController into some other name just in case. Didn't work.

UPD5: Before UPD1 it looked like this:

controller.pushViewController(controller, animated: true)

Instead of posting an image can you please share entire crash log? Specially the line where it says "terminating app due to uncaught exception" (if that exists). — Adeel Miraj, Aug 07 '19 at 09:28
@Adeel alright, posted it in the UPD2 section of the question — Isaaс Weisberg, Aug 07 '19 at 09:44

score 1 · Accepted Answer · answered Aug 07 '19 at 10:50

1

As stated in UPD5, the controller you are pushing into the navigation controller is literally that same controller itself.

answered Aug 07 '19 at 10:50

Isaaс Weisberg

2,296
2
12
28

Andy Darwin · Answer 2 · 2019-08-07T11:42:37.327

0

Check this stackOverflow

The crash info is obscure. Hope it can inspire you.

edited Aug 07 '19 at 11:42

answered Aug 07 '19 at 09:55

Andy Darwin

478
5
19

Nope, this statement is unfortunately invalid. Missing outlets always result in an unrecognized key exception while trying to KVC, usually in `-[NSObject+ (NSKeyValueCoding) setValue:forKey:]`, which gets called in a course of `-[UIViewController loadView]`. This method might be called both before and after a modal presentation/nav controller push and thus this failure is independent of view controllers state. – Isaaс Weisberg Aug 07 '19 at 10:02
Spoiler: I know this for certain because I just happen to have a crash log where this exact case happened, unrelated to the flow in question. – Isaaс Weisberg Aug 07 '19 at 10:03
No idea. Check this and maybe it can inspire you. https://stackoverflow.com/questions/26442414/libcabi-dylib-terminating-with-uncaught-exception-of-type-nsexception-lldb – Andy Darwin Aug 07 '19 at 11:41

UINavigationController push crash

2 Answers2