如何在FirebaseUI上设置首选国家/地区？

Question

我希望英国成为phoneProvider的默认国家/地区，如何进行预设？我在authUI上找不到任何可以使我做到这一点的属性。

 class Login: UIViewController, FUIAuthDelegate {
    let authUI = FUIAuth.defaultAuthUI()

   override func viewDidAppear(_ animated: Bool) {

    authUI?.delegate = self
    let phoneProvider = FUIPhoneAuth(authUI: authUI!)
    authUI!.isSignInWithEmailHidden = true
    authUI!.providers = [phoneProvider]
    phoneProvider.signIn(withPresenting: self, phoneNumber: nil)
     }
 }