Where to use popToRootViewController to pop extra VC off stack? - ios

Question

I have a view controller with two buttons:
Button1 brings up the documentPickerViewController and lets user pick a file.
Button2 goes to a second view controller.
Button1 is linked to "openFile" in the code below.
Button2 calls the segue to the second view controller.
So this is how I get the problem:
Click Button1, document picker shows up.
If I pick a document, then document picker disappears and I'm back to view controller.
So far so good.
Now I press Button2. Second view controller shows up. All good. I exit and go back to 1st view controller.
Now I press Button1 again. Document picker shows up.
But this time I click "cancel". Document picker disappears but the SECOND view controller appears!
I get
"Unbalanced calls to begin/end appearance transitions for <_UIWaitingForRemoteViewContainerViewController: 0x122206480>." and
"[DocumentManager] The view service did terminate with error: Error Domain=_UIViewServiceErrorDomain Code=1 "(null)" UserInfo={Terminated=disconnect method}"
From researching I understand that I must have popped an extra 2nd view controller to the stack but I can't see where I would have done it and also where would be the appropriate place to pop it?
I've tried setting "animated: false" and that didn't make any difference.
Thanks in advance.
#IBAction func openFile(_ sender: Any) {
let documentPicker: UIDocumentPickerViewController = UIDocumentPickerViewController(documentTypes: ["public.text"], in: UIDocumentPickerMode.import)
documentPicker.delegate = self
documentPicker.modalPresentationStyle = UIModalPresentationStyle.fullScreen
self.present(documentPicker, animated: true, completion: nil)
}
func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
self.dismiss(animated: true, completion: nil)
}
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
if controller.documentPickerMode == UIDocumentPickerMode.import {
var textRead = ""
do {
if urls.count > 0 {
for i in 0...urls.count-1 {
textRead = try String(contentsOf: urls[i], encoding: .utf8)
textView.text = textView.text + textRead
}
}
}
catch {
/* error handling here */
print("There's a problem reading the file")
}
}
}

Answer 1

I'm not sure what you want to do in your implementation of documentPickerWasCancelled(_:) but know that if you just want to hide the document picker, you don't need to explicitely call self.dismiss(animated: true, completion: nil): when you tap 'Cancel' the document picker dismisses itself already.

Answer 2

After more experimenting and researching, I found this stopped the 2nd view controller from appearing, even though the two error messages are still appearing:
func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
//self.dismiss(animated: true, completion: nil)
self.navigationController?.popToRootViewController(animated: true)
}
Would still appreciate if someone can suggest a more elegant solution which eliminates the error messages altogether.
EDIT:
After playing with it a bit more, I found the fix!
We only need this:
func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
// do nothing. The picker is dismissed anyway.
}
So the dismiss statement was causing the problem. By leaving out any dismiss picker call, the picker window closes anyway.