Warning: Attempt to present vc whose view is not in the window hierarchy

Question

So I'm attempting to a cue a segue from a model VC to run on the root VC however when I attempt to do so it gives me this error - Warning: Attempt to present vc whose view is not in the window hierarchy. I tried the viewWIllAppear() but that also doesn't work because my VC only covers half the root vc's view as it is a side menu. However, after cueing a segue directly from the root VC it works fine.

this is the code that I have rn:

dismiss(animated: true) {

    let vc = self.storyboard?.instantiateViewController(withIdentifier: "MainViewController") as? MainViewController
    vc?.performSegue(withIdentifier: "ToSubmition", sender: self)

}

Answer 1

Try dismissing the view controller first:

dismiss(animated: true) {

    self.dismiss(animated: true) { 
        self.performSegue(withIdentifier: "ToSubmition", sender: self)
    }
}

Answer 2

I think you're trying to present a VC from your side menu, which of course can't be done as the view is not in the window's hierarchy. What you can do is to make use of NSNotificationCenter to post a notification key once the function is called and dismiss your side menu. Then in your Main VC, add an observer and create a function to perform your intended segue.

You can read from the Apple API reference on how to implement NSNotification Center.

Answer 3

• Completion handlers always uses the background thread, to do UI updates or something like yours use main thread

  dismiss(animated: true) {
    DispatchQueue.main.async {
      let vc = self.storyboard?.instantiateViewController(withIdentifier: "MainViewController") as? MainViewController
      vc?.performSegue(withIdentifier: "ToSubmition", sender: self)
    }
  }
  

• If it fails use dispatch_after and set some delay before performing segue.

  dismiss(animated: true) {
    let mainQueue = DispatchQueue.main
    let deadline = DispatchTime.now() + .seconds(5)
    mainQueue.asyncAfter(deadline: deadline) {
       // ...perform segue
    }
  }
  

• It is a blind shot give it a try.

Answer 4

Ok so I figured it out. you couldn't call another view controller by creating an instance. instead I just called the present VC at the time

dismiss(animated: true) {
        if let mainView = UIApplication.shared.keyWindow?.rootViewController as? MainViewController {
            mainView.ToSubmition()
        }
    }