將多個驗證供應商連結至 Apple 平台的帳戶

您可以將驗證供應商憑證連結至現有使用者帳戶，允許使用者透過多個驗證供應商登入應用程式。無論使用者透過哪個驗證提供者登入，系統都會使用相同的 Firebase 使用者 ID 識別使用者。舉例來說，以密碼登入的使用者可以連結 Google 帳戶，日後就能透過任一方法登入。或者，匿名使用者可以連結 Facebook 帳戶，然後稍後使用 Facebook 登入，繼續使用您的應用程式。

事前準備

在應用程式中新增對兩個以上驗證供應商的支援 (可能包括匿名驗證)。

如要將驗證供應商憑證連結至現有使用者帳戶，請按照下列步驟操作：

  1. 使用任何驗證供應商或方法登入使用者。
  2. 完成新驗證供應商的登入流程，但不要呼叫 FIRAuth.signInWith 方法。例如，取得使用者的 Google ID 權杖、Facebook 存取權杖，或是電子郵件和密碼。

  3. 取得新驗證供應商的 FIRAuthCredential：

    Google 登入
    Swift
    guard   let authentication = user?.authentication,   let idToken = authentication.idToken else {   return }  let credential = GoogleAuthProvider.credential(withIDToken: idToken,                                                accessToken: authentication.accessToken)
    Objective-C
    FIRAuthCredential *credential = [FIRGoogleAuthProvider credentialWithIDToken:result.user.idToken.tokenString                                  accessToken:result.user.accessToken.tokenString];
    Facebook 登入
    Swift
    let credential = FacebookAuthProvider   .credential(withAccessToken: AccessToken.current!.tokenString)
    Objective-C
    FIRAuthCredential *credential = [FIRFacebookAuthProvider     credentialWithAccessToken:[FBSDKAccessToken currentAccessToken].tokenString];
    使用電子郵件地址和密碼登入
    Swift
    let credential = EmailAuthProvider.credential(withEmail: email, password: password)
    Objective-C
    FIRAuthCredential *credential =     [FIREmailAuthProvider credentialWithEmail:email                                              password:password];

  4. 將 FIRAuthCredential 物件傳遞至已登入使用者的 linkWithCredential:completion: 方法：

    Swift
        user.link(with: credential) { authResult, error in   // ... } }
    Objective-C
        [[FIRAuth auth].currentUser linkWithCredential:credential     completion:^(FIRAuthDataResult *result, NSError *_Nullable error) {   // ... }];

    如果憑證已連結至其他使用者帳戶，對 linkWithCredential:completion: 的呼叫就會失敗。在這種情況下，您必須視應用程式需求，處理帳戶和相關聯資料的合併作業：

    Swift

    let prevUser = Auth.auth().currentUser Auth.auth().signIn(with: credential) { authResult, error in     if let error = error {       let authError = error as NSError       if isMFAEnabled, authError.code == AuthErrorCode.secondFactorRequired.rawValue {         // The user is a multi-factor user. Second factor challenge is required.         let resolver = authError           .userInfo[AuthErrorUserInfoMultiFactorResolverKey] as! MultiFactorResolver         var displayNameString = ""         for tmpFactorInfo in resolver.hints {           displayNameString += tmpFactorInfo.displayName ?? ""           displayNameString += " "         }         self.showTextInputPrompt(           withMessage: "Select factor to sign in\n\(displayNameString)",           completionBlock: { userPressedOK, displayName in             var selectedHint: PhoneMultiFactorInfo?             for tmpFactorInfo in resolver.hints {               if displayName == tmpFactorInfo.displayName {                 selectedHint = tmpFactorInfo as? PhoneMultiFactorInfo               }             }             PhoneAuthProvider.provider()               .verifyPhoneNumber(with: selectedHint!, uiDelegate: nil,                                  multiFactorSession: resolver                                    .session) { verificationID, error in                 if error != nil {                   print(                     "Multi factor start sign in failed. Error: \(error.debugDescription)"                   )                 } else {                   self.showTextInputPrompt(                     withMessage: "Verification code for \(selectedHint?.displayName ?? "")",                     completionBlock: { userPressedOK, verificationCode in                       let credential: PhoneAuthCredential? = PhoneAuthProvider.provider()                         .credential(withVerificationID: verificationID!,                                     verificationCode: verificationCode!)                       let assertion: MultiFactorAssertion? = PhoneMultiFactorGenerator                         .assertion(with: credential!)                       resolver.resolveSignIn(with: assertion!) { authResult, error in                         if error != nil {                           print(                             "Multi factor finanlize sign in failed. Error: \(error.debugDescription)"                           )                         } else {                           self.navigationController?.popViewController(animated: true)                         }                       }                     }                   )                 }               }           }         )       } else {         self.showMessagePrompt(error.localizedDescription)         return       }       // ...       return     }     // User is signed in     // ... }             // Merge prevUser and currentUser accounts and data             // ...         }

    Objective-C

    FIRUser *prevUser = [FIRAuth auth].currentUser; [[FIRAuth auth] signInWithCredential:credential                           completion:^(FIRAuthDataResult * _Nullable authResult,                                        NSError * _Nullable error) {     if (isMFAEnabled && error && error.code == FIRAuthErrorCodeSecondFactorRequired) {       FIRMultiFactorResolver *resolver = error.userInfo[FIRAuthErrorUserInfoMultiFactorResolverKey];       NSMutableString *displayNameString = [NSMutableString string];       for (FIRMultiFactorInfo *tmpFactorInfo in resolver.hints) {         [displayNameString appendString:tmpFactorInfo.displayName];         [displayNameString appendString:@" "];       }       [self showTextInputPromptWithMessage:[NSString stringWithFormat:@"Select factor to sign in\n%@", displayNameString]                            completionBlock:^(BOOL userPressedOK, NSString *_Nullable displayName) {        FIRPhoneMultiFactorInfo* selectedHint;        for (FIRMultiFactorInfo *tmpFactorInfo in resolver.hints) {          if ([displayName isEqualToString:tmpFactorInfo.displayName]) {            selectedHint = (FIRPhoneMultiFactorInfo *)tmpFactorInfo;          }        }        [FIRPhoneAuthProvider.provider         verifyPhoneNumberWithMultiFactorInfo:selectedHint         UIDelegate:nil         multiFactorSession:resolver.session         completion:^(NSString * _Nullable verificationID, NSError * _Nullable error) {           if (error) {             [self showMessagePrompt:error.localizedDescription];           } else {             [self showTextInputPromptWithMessage:[NSString stringWithFormat:@"Verification code for %@", selectedHint.displayName]                                  completionBlock:^(BOOL userPressedOK, NSString *_Nullable verificationCode) {              FIRPhoneAuthCredential *credential =                  [[FIRPhoneAuthProvider provider] credentialWithVerificationID:verificationID                                                               verificationCode:verificationCode];              FIRMultiFactorAssertion *assertion = [FIRPhoneMultiFactorGenerator assertionWithCredential:credential];              [resolver resolveSignInWithAssertion:assertion completion:^(FIRAuthDataResult * _Nullable authResult, NSError * _Nullable error) {                if (error) {                  [self showMessagePrompt:error.localizedDescription];                } else {                  NSLog(@"Multi factor finanlize sign in succeeded.");                }              }];            }];           }         }];      }];     }   else if (error) {     // ...     return;   }   // User successfully signed in. Get user data from the FIRUser object   if (authResult == nil) { return; }   FIRUser *user = authResult.user;   // ... }];                                     // Merge prevUser and currentUser accounts and data                                     // ...                                 }];

如果對 linkWithCredential:completion: 的呼叫成功，使用者現在就能使用任何已連結的驗證供應商登入，並存取相同的 Firebase 資料。

您可以取消驗證供應商與帳戶的連結，這樣使用者就無法再透過該供應商登入。

如要取消授權提供者與使用者帳戶的連結，請將提供者 ID 傳遞至 unlink 方法。您可以從 providerData 屬性取得連結至使用者的驗證供應商 ID。

Swift

Auth.auth().currentUser?.unlink(fromProvider: providerID!) { user, error in   // ... }

Objective-C

[[FIRAuth auth].currentUser unlinkFromProvider:providerID                                     completion:^(FIRUser *_Nullable user, NSError *_Nullable error) {   // ... }];

疑難排解

如果嘗試連結多個帳戶時發生錯誤，請參閱已驗證電子郵件地址的說明文件。