How can I change the choices in a pickerview based on another pickervew?

Picture of current versionI currently have two picker views. Ones a country picker view(US and Canada) and the other is a state picker view. I'd like to have it so when USA is selected it displays US states, and when Canada is selected, Canadian provinces are displayed. Here is a sample of what I have so far. Help would be very much appreciated!

let countries = ["",
"USA",
"Canada",
]
let states = ["Alaska",
"Alabama",
"Arkansas"]
 let provinces = ["Alberta",
"British Columbia",
"Manitoba",
"New Brunswick"]

//Sets picker view
let pickerView = UIPickerView()
//Holds current data in array
var currentArray: [String] = []
//Holds current text field
var activeTextField : UITextField!
var activeField: UITextField?

 fileprivate func delegates() {
  countryTextView.delegate = self
  stateTextView.delegate = self
}

fileprivate func pickerViewDelegates() {
    //Enables pickerview
    pickerView.delegate = self
    pickerView.dataSource = self
}
//Sets pickerview input
fileprivate func pickerViewSet() {
    countryTextView.inputView = pickerView
    stateTextView.inputView = pickerView
}
//Closes keyboard when done button is pressed
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    textField.resignFirstResponder()
    return true
}
//Textfield delegate
func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
    activeTextField = textField

    switch textField {
    case countryTextView:
        currentArray = countries
    case stateTextView:
        currentArray = states
    default:
        print("Default")
    }
    pickerView.reloadAllComponents()
    return true
}
//Number of rows in picker view
func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
}
//One element of array per row
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return currentArray.count
}
//Puts the array element of whichever picker view is chosen into picker view
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?{
    return currentArray[row]
}
//Selects the array element in the row thats chosen
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    print("Selected item is", currentArray[row])
    activeTextField.text = currentArray[row]
}