dismissing the keyboard on UIAlertController UITextField - swift

Question

normally view.endEditing(true) always removes the keyboard in swift on iOS.
however this is not always true, like when the UITextField is part of a self.present()'ed modal view i.e. a form inside a UIAlertController
Example
let alert = UIAlertController(title: _title, message: "Choose", preferredStyle: .alert)
let numberLabel = UILabel(frame: CGRect(x:10, y:0, width:90, height:20))
numberLabel.textColor = .black
numberLabel.textAlignment = NSTextAlignment.left
numberLabel.font = UIFont(name: titleLabel.font.fontName, size: 16)
numberLabel.font = UIFont.boldSystemFont(ofSize: titleLabel.font.pointSize)
numberLabel.text = "Quantity"
let quantityField = UITextField(frame: CGRect(x:100, y:0, width:140, height:25))
quantityField.layer.borderWidth = 1
quantityField.keyboardType = .numberPad
quantityField.layer.borderColor = UIColor.lightGray.cgColor
quantityField.delegate = self
self.addDoneButtonOnKeyboard(textField: quantityField)
self.present(alert, animated: true, completion: nil)
now in this self.addDoneButtonOnKeyboard method I have this nifty code
func addDoneButtonOnKeyboard(textField: UITextField){
let doneToolbar: UIToolbar = UIToolbar(frame: CGRect(x:0, y:0, width:320, height:50))
doneToolbar.barStyle = UIBarStyle.default
let flexSpace = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.flexibleSpace, target: nil, action: nil)
let done: UIBarButtonItem = UIBarButtonItem(title: "Done", style: UIBarButtonItemStyle.done, target: self, action: #selector(ViewControllerDisplay.doneButtonAction(_:)))
let items = NSMutableArray()
items.add(flexSpace)
items.add(done)
doneToolbar.items = items as? [UIBarButtonItem]
doneToolbar.sizeToFit()
textField.inputAccessoryView = doneToolbar
}
#objc func doneButtonAction(_ btn: UIBarButtonItem){
view.endEditing(true)
}
the purpose of all this is so that a "Done" keyboard button appears. It does. In fact it looks great, I can also capture the doneButtonAction() event which is great, but I am only capturing the UIBarButtonItem so I can't use UITextField.resignFirstResponder() method, even though I know it will work. I have to use "view"
What I want to do is call alert.endEditting(true) but I've tried cycling through the subviews, screening for any occurrences of UIAlertController but self.present doesn't work that way
Can anyone help me clear this keyboard off the alert view?

Answer 1

I fixed it by getting the topMost view Controller, and calling endEditing(true) I think this question should remain up it's quite a useful titbit for someone one day
#objc func doneButtonAction(_ btn: UIBarButtonItem){
if var topController = UIApplication.shared.keyWindow?.rootViewController {
while let presentedViewController = topController.presentedViewController {
topController = presentedViewController
}
topController.view.endEditing(true)
}
}