DateDurationPicker.swift

func numberOfComponents(in pickerView: UIPickerView) -> Int {
  return 2
}
        
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
  return component == 0 ? values.count : units.count
}
        
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
  if component == 0 {
    return "\(values[row])"
  }
  else {
    return units[row].rawValue
  }
}
        
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
  let valueIndex = pickerView.selectedRow(inComponent: 0)
  let unitIndex = pickerView.selectedRow(inComponent: 1)
  selection.wrappedValue = DateDuration(value: values[valueIndex], unit: units[unitIndex])
}