UINavigationControllerのBackButtonのタイトルを一括で変更

HogeNavigationController.swift

class HogeNavigationController: UINavigationController, UINavigationControllerDelegate {

  override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self;  // delegateセット
  }

  // MARK: UINavigationControllerDelegate
  func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
    let backButton: UIBarButtonItem = UIBarButtonItem()
    backButton.title = ""
    viewController.navigationItem.backBarButtonItem = backButton;
  }
}