how to override viewWillDisappear in Swift3

Your code will look like

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    // Hide the navigation bar on the this view controller
    self.navigationController?.setNavigationBarHidden(true, animated: true)
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    // Show the navigation bar on other view controllers
    self.navigationController?.setNavigationBarHidden(false, animated: true)
}