how to create referencing outlet to ScrollView without getting key value coding-compliant error

Question

So from a working state, if I ad a referencing outlet from my scroll view to the controller it is in, I crash at run-time from

Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UIViewController 0x7fb3bd7635b0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key taskDetailScrollView.'

class TaskDetailController : UIViewController {
     @IBOutlet weak var taskDetailScrollView: UIScrollView!

override func viewDidLoad(){
    let contentRect: CGRect = taskDetailScrollView.subviews.reduce(into: .zero) { rect, view in
        rect = rect.union(view.frame)
    }
    taskDetailScrollView.contentSize = contentRect.size
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if (segue.identifier == "TaskDetailTableEmbedSegue") {
        segue.destination.view.translatesAutoresizingMaskIntoConstraints = false;
    }
}

I don't see why this referencing outlet is different from the dozens of others I've done.

I'm wondering if I violated some layout constraint rule, but I don't see why that would relate to this.

Very bizarre, but if I delete the referencing outlet then it runs fine. But I need a referencing outlet. Also interface builder recognizes the outlet connection and fills in the circle, so why does it have an issue?

   TitleBarView
   MainSectionView
       ScrollView
       ButtonView
   BottomBarView

Answer 1

The issue was that somehow the controller's inherit module from target had become undone.

I am kind of surprised that any wiring can be done if it cannot even find the controller class. The error itself is a bit cryptic as it makes it sound as if it is an IBOutlet error rather than the controller itself not being found.