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    // MARK: hide status bar
    override var preferredStatusBarStyle : UIStatusBarStyle {
        return UIStatusBarStyle.lightContent
    }

func getAge() -> Int? {
    let ageComponents = Calendar.current.dateComponents([.year], from: birthdayPicker.date, to: Date())
    return ageComponents.year
}

// Set picker current date 
    birthdayPicker.maximumDate = Date()

// Đóng keyboard sau khi nhập
// #1
    nameTextField.delegate = self
    workTextField.delegate = self
    
extension ViewController: UITextFieldDelegate{
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
}

// #2
// dismiss keyboard viewdidload
    self.view.addGestureRecognizer(UITapGestureRecognizer(target: self.view, action: Selector.endEditing))
    
// in helper file
extension Selector {
    static let endEditing = #selector(UIView.endEditing(_:))
}

// #3
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    view.endEditing(true)
}

// Show Alert

// Helper file
extension UIViewController {
    func showAlert(title: String, message: String, buttonTitle: String) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: buttonTitle, style: .default, handler: nil))
        present(alert, animated: true, completion: nil)
    }
}

// View
showAlert(title: "Info is miss or invalid", message: "Please fill out correct presonal info", buttonTitle: "OK")