Authenticate Using Twitter on Apple Platforms

You can let your users authenticate with Firebase using OAuth providers like Twitter by integrating generic OAuth Login into your app using the Firebase SDK to carry out the end to end sign-in flow.

Before you begin

Use Swift Package Manager to install and manage Firebase dependencies.

1. In Xcode, with your app project open, navigate to File > Add Packages .
2. When prompted, add the Firebase Apple platforms SDK repository:

https://github.com/firebase/firebase-ios-sdk.git

3. Choose the Firebase Authentication library.
4. Add the -ObjC flag to the Other Linker Flags section of your target's build settings.
5. When finished, Xcode will automatically begin resolving and downloading your dependencies in the background.

To sign in users using Twitter accounts, you must first enable Twitter as a sign-in provider for your Firebase project:

1. Add Firebase to your Apple project .

2. Include the following pods in your Podfile :

   pod 'FirebaseAuth'

3. In the Firebase console , open the Auth section.
4. On the Sign in method tab, enable the Twitter provider.
5. Add the API key and API secret from that provider's developer console to the provider configuration:
   1. Register your app as a developer application on Twitter and get your app's OAuth API key and API secret .
   2. Make sure your Firebase OAuth redirect URI (e.g. my-app-12345.firebaseapp.com/__/auth/handler ) is set as your Authorization callback URL in your app's settings page on your Twitter app's config .
6. Click Save .

Handle the sign-in flow with the Firebase SDK

To handle the sign-in flow with the Firebase Apple platforms SDK, follow these steps:

1. Add custom URL schemes to your Xcode project:

   1. Open your project configuration: double-click the project name in the left tree view. Select your app from the TARGETS section, then select the Info tab, and expand the URL Types section.
   2. Click the + button, and add your Encoded App ID as a URL scheme. You can find your Encoded App ID on the General Settings page of the Firebase console, in the section for your iOS app. Leave the other fields blank.

      When completed, your config should look something similar to the following (but with your application-specific values):

      

2. Create an instance of an OAuthProviderusing the provider ID twitter.com.

   Swift

     
    var 
     
    provider 
     
    = 
     
    OAuthProvider 
    ( 
    providerID 
    : 
     
    "twitter.com" 
    ) 
     
   

   Objective-C

     
    FIROAuthProvider 
     
    * 
    provider 
     
    = 
     
    [ 
    FIROAuthProvider 
     
    providerWithProviderID 
    : 
    @"twitter.com" 
    ]; 
     
   

3. Optional: Specify additional custom OAuth parameters that you want to send with the OAuth request.

   Swift

     
    provider 
    . 
    customParameters 
     
    = 
     
    [ 
     
    "lang" 
    : 
     
    "fr" 
     
    ] 
     
   

   Objective-C

     
    [ 
    provider 
     
    setCustomParameters 
    : 
    @{ 
    @"lang" 
    : 
     
    @"fr" 
    } 
    ]; 
     
   

   For the parameters Twitter supports, see the Twitter OAuth documentation . Note that you can't pass Firebase-required parameters with setCustomParameters . These parameters are client_id, redirect_uri, response_type, scopeand state.

4. Optional: If you want to customize the way your app presents the SFSafariViewController or UIWebView when displaying the reCAPTCHA to the user, create a custom class that conforms to the AuthUIDelegate protocol, and pass it to credentialWithUIDelegate .

5. Authenticate with Firebase using the OAuth provider object.

   Swift

     
    provider 
    . 
    getCredentialWith 
    ( 
    nil 
    ) 
     
    { 
     
    credential 
    , 
     
    error 
     
    in 
     
    if 
     
    error 
     
    != 
     
    nil 
     
    { 
     
    // Handle error. 
     
    } 
     
    if 
     
    credential 
     
    != 
     
    nil 
     
    { 
     
    Auth 
    . 
    auth 
    (). 
    signIn 
    ( 
    with 
    : 
     
    credential 
    ) 
     
    { 
     
    authResult 
    , 
     
    error 
     
    in 
     
    if 
     
    error 
     
    != 
     
    nil 
     
    { 
     
    // Handle error. 
     
    } 
     
    // User is signed in. 
     
    // IdP data available in authResult.additionalUserInfo.profile. 
     
    // Twitter OAuth access token can also be retrieved by: 
     
    // (authResult.credential as? OAuthCredential)?.accessToken 
     
    // Twitter OAuth ID token can be retrieved by calling: 
     
    // (authResult.credential as? OAuthCredential)?.idToken 
     
    // Twitter OAuth secret can be retrieved by calling: 
     
    // (authResult.credential as? OAuthCredential)?.secret 
     
    } 
     
    } 
     
    } 
     
   

   Objective-C

     
    [ 
    provider 
     
    getCredentialWithUIDelegate 
    : 
    nil 
     
    completion 
    : 
    ^ 
    ( 
    FIRAuthCredential 
     
    * 
    _Nullable 
     
    credential 
    , 
     
    NSError 
     
    * 
    _Nullable 
     
    error 
    ) 
     
    { 
     
    if 
     
    ( 
    error 
    ) 
     
    { 
     
    // Handle error. 
     
    } 
     
    if 
     
    ( 
    credential 
    ) 
     
    { 
     
    [[ 
    FIRAuth 
     
    auth 
    ] 
     
    signInWithCredential 
    : 
    credential 
     
    completion 
    : 
    ^ 
    ( 
    FIRAuthDataResult 
     
    * 
    _Nullable 
     
    authResult 
    , 
     
    NSError 
     
    * 
    _Nullable 
     
    error 
    ) 
     
    { 
     
    if 
     
    ( 
    error 
    ) 
     
    { 
     
    // Handle error. 
     
    } 
     
    // User is signed in. 
     
    // IdP data available in authResult.additionalUserInfo.profile. 
     
    // Twitter OAuth access token can also be retrieved by: 
     
    // authResult.credential.accessToken 
     
    // Twitter OAuth ID token can be retrieved by calling: 
     
    // authResult.credential.idToken 
     
    // Twitter OAuth secret can be retrieved by calling: 
     
    // authResult.credential.secret 
     
    }]; 
     
    } 
     
    }]; 
     
   

   Using the OAuth access token, you can call the Twitter API .

   For example, to get basic profile information, you can call the REST API, passing the access token in the Authorization header:

   https://api.twitter.com/labs/1/users?usernames=TwitterDev

6. While the above examples focus on sign-in flows, you also have the ability to link a Twitter provider to an existing user. For example, you can link multiple providers to the same user allowing them to sign in with either.

   Swift

     
    Auth 
    (). 
    currentUser 
    . 
    link 
    ( 
    withCredential 
    : 
     
    credential 
    ) 
     
    { 
     
    authResult 
    , 
     
    error 
     
    in 
     
    if 
     
    error 
     
    != 
     
    nil 
     
    { 
     
    // Handle error. 
     
    } 
     
    // Twitter credential is linked to the current user. 
     
    // IdP data available in authResult.additionalUserInfo.profile. 
     
    // Twitter OAuth access token can also be retrieved by: 
     
    // (authResult.credential as? OAuthCredential)?.accessToken 
     
    // Twitter OAuth ID token can be retrieved by calling: 
     
    // (authResult.credential as? OAuthCredential)?.idToken 
     
    // Twitter OAuth secret can be retrieved by calling: 
     
    // (authResult.credential as? OAuthCredential)?.secret 
     
    } 
     
   

   Objective-C

     
    [[ 
    FIRAuth 
     
    auth 
    ]. 
    currentUser 
     
    linkWithCredential 
    : 
    credential 
     
    completion 
    : 
    ^ 
    ( 
    FIRAuthDataResult 
     
    * 
     
    _Nullable 
     
    authResult 
    , 
     
    NSError 
     
    * 
     
    _Nullable 
     
    error 
    ) 
     
    { 
     
    if 
     
    ( 
    error 
    ) 
     
    { 
     
    // Handle error. 
     
    } 
     
    // Twitter credential is linked to the current user. 
     
    // IdP data available in authResult.additionalUserInfo.profile. 
     
    // Twitter OAuth access token is can also be retrieved by: 
     
    // ((FIROAuthCredential *)authResult.credential).accessToken 
     
    // Twitter OAuth ID token can be retrieved by calling: 
     
    // ((FIROAuthCredential *)authResult.credential).idToken 
     
    // Twitter OAuth secret can be retrieved by calling: 
     
    // ((FIROAuthCredential *)authResult.credential).secret 
     
    }]; 
     
   

7. The same pattern can be used with reauthenticateWithCredential which can be used to retrieve fresh credentials for sensitive operations that require recent login.

   Swift

     
    Auth 
    (). 
    currentUser 
    . 
    reauthenticateWithCredential 
    ( 
    withCredential 
    : 
     
    credential 
    ) 
     
    { 
     
    authResult 
    , 
     
    error 
     
    in 
     
    if 
     
    error 
     
    != 
     
    nil 
     
    { 
     
    // Handle error. 
     
    } 
     
    // User is re-authenticated with fresh tokens minted and 
     
    // should be able to perform sensitive operations like account 
     
    // deletion and email or password update. 
     
    // IdP data available in result.additionalUserInfo.profile. 
     
    // Additional OAuth access token is can also be retrieved by: 
     
    // (authResult.credential as? OAuthCredential)?.accessToken 
     
    // Twitter OAuth ID token can be retrieved by calling: 
     
    // (authResult.credential as? OAuthCredential)?.idToken 
     
    // Twitter OAuth secret can be retrieved by calling: 
     
    // (authResult.credential as? OAuthCredential)?.secret 
     
    } 
     
   

   Objective-C

     
    [[ 
    FIRAuth 
     
    auth 
    ]. 
    currentUser 
     
    reauthenticateWithCredential 
    : 
    credential 
     
    completion 
    : 
    ^ 
    ( 
    FIRAuthDataResult 
     
    * 
     
    _Nullable 
     
    authResult 
    , 
     
    NSError 
     
    * 
     
    _Nullable 
     
    error 
    ) 
     
    { 
     
    if 
     
    ( 
    error 
    ) 
     
    { 
     
    // Handle error. 
     
    } 
     
    // User is re-authenticated with fresh tokens minted and 
     
    // should be able to perform sensitive operations like account 
     
    // deletion and email or password update. 
     
    // IdP data available in result.additionalUserInfo.profile. 
     
    // Additional OAuth access token is can also be retrieved by: 
     
    // ((FIROAuthCredential *)authResult.credential).accessToken 
     
    // Twitter OAuth ID token can be retrieved by calling: 
     
    // ((FIROAuthCredential *)authResult.credential).idToken 
     
    // Twitter OAuth secret can be retrieved by calling: 
     
    // ((FIROAuthCredential *)authResult.credential).secret 
     
    }]; 
     
   

  
 // Sign-in with an OAuth credential. 
  
 provider 
 . 
 getCredentialWith 
 ( 
 nil 
 ) 
  
 { 
  
 credential 
 , 
  
 error 
  
 in 
  
 // An account with the same email already exists. 
  
 if 
  
 ( 
 error 
  
 as 
  
 NSError 
 ?)?. 
 code 
  
 == 
  
 AuthErrorCode 
 . 
 accountExistsWithDifferentCredential 
 . 
 rawValue 
  
 { 
  
 // Get pending credential and email of existing account. 
  
 let 
  
 existingAcctEmail 
  
 = 
  
 ( 
 error 
 ! 
  
 as 
  
 NSError 
 ). 
 userInfo 
 [ 
 AuthErrorUserInfoEmailKey 
 ] 
  
 as 
 ! 
  
 String 
  
 let 
  
 pendingCred 
  
 = 
  
 ( 
 error 
 ! 
  
 as 
  
 NSError 
 ). 
 userInfo 
 [ 
 AuthErrorUserInfoUpdatedCredentialKey 
 ] 
  
 as 
 ! 
  
 AuthCredential 
  
 // Lookup existing account identifier by the email. 
  
 Auth 
 . 
 auth 
 (). 
 fetchProviders 
 ( 
 forEmail 
 : 
 existingAcctEmail 
 ) 
  
 { 
  
 providers 
 , 
  
 error 
  
 in 
  
 // Existing email/password account. 
  
 if 
  
 ( 
 providers 
 ?. 
 contains 
 ( 
 EmailAuthProviderID 
 )) 
 ! 
  
 { 
  
 // Existing password account for email. Ask user to provide the password of the 
  
 // existing account. 
  
 // Sign in with existing account. 
  
 Auth 
 . 
 auth 
 (). 
 signIn 
 ( 
 withEmail 
 : 
 existingAcctEmail 
 , 
  
 password 
 : 
 password 
 ) 
  
 { 
  
 user 
 , 
  
 error 
  
 in 
  
 // Successfully signed in. 
  
 if 
  
 user 
  
 != 
  
 nil 
  
 { 
  
 // Link pending credential to account. 
  
 Auth 
 . 
 auth 
 (). 
 currentUser 
 ?. 
 linkAndRetrieveData 
 ( 
 with 
 : 
  
 pendingCred 
 ) 
  
 { 
  
 result 
 , 
  
 error 
  
 in 
  
 // ... 
  
 } 
  
 } 
  
 } 
  
 } 
  
 } 
  
 return 
  
 } 
  
 // Other errors. 
  
 if 
  
 error 
  
 != 
  
 nil 
  
 { 
  
 // handle the error. 
  
 return 
  
 } 
  
 // Sign in with the credential. 
  
 if 
  
 credential 
  
 != 
  
 nil 
  
 { 
  
 Auth 
 . 
 auth 
 (). 
 signInAndRetrieveData 
 ( 
 with 
 : 
  
 credential 
 !) 
  
 { 
  
 result 
 , 
  
 error 
  
 in 
  
 if 
  
 error 
  
 != 
  
 nil 
  
 { 
  
 // handle the error. 
  
 return 
  
 } 
  
 } 
  
 } 
  
 } 
  

  
 // Sign-in with an OAuth credential. 
  
 [ 
 provider 
  
 getCredentialWithUIDelegate 
 : 
 nil 
  
 completion 
 : 
 ^ 
 ( 
 FIRAuthCredential 
  
 * 
 _Nullable 
  
 credential 
 , 
  
 NSError 
  
 * 
 _Nullable 
  
 error 
 ) 
  
 { 
  
 // An account with the same email already exists. 
  
 if 
  
 ( 
 error 
 . 
 code 
  
 == 
  
 FIRAuthErrorCodeAccountExistsWithDifferentCredential 
 ) 
  
 { 
  
 // Get pending credential and email of existing account. 
  
 NSString 
  
 * 
 existingAcctEmail 
  
 = 
  
 error 
 . 
 userInfo 
 [ 
 FIRAuthErrorUserInfoEmailKey 
 ]; 
  
 FIRAuthCredential 
  
 * 
 pendingCred 
  
 = 
  
 error 
 . 
 userInfo 
 [ 
 FIRAuthErrorUserInfoUpdatedCredentialKey 
 ]; 
  
 // Lookup existing account identifier by the email. 
  
 [[ 
 FIRAuth 
  
 auth 
 ] 
  
 fetchProvidersForEmail 
 : 
 existingAcctEmail 
  
 completion 
 : 
 ^ 
 ( 
 NSArray<NSString 
  
 * 
>  
 * 
 _Nullable 
  
 providers 
 , 
  
 NSError 
  
 * 
 _Nullable 
  
 error 
 ) 
  
 { 
  
 // Existing email/password account. 
  
 if 
  
 ( 
  
 [ 
 providers 
  
 containsObject 
 : 
 FIREmailAuthProviderID 
 ] 
  
 ) 
  
 { 
  
 // Existing password account for email. Ask user to provide the password of the 
  
 // existing account. 
  
 // Sign in with existing account. 
  
 [[ 
 FIRAuth 
  
 auth 
 ] 
  
 signInWithEmail 
 : 
 existingAcctEmail 
  
 password 
 : 
 password 
  
 completion 
 : 
 ^ 
 ( 
 FIRUser 
  
 * 
 user 
 , 
  
 NSError 
  
 * 
 error 
 ) 
  
 { 
  
 // Successfully signed in. 
  
 if 
  
 ( 
 user 
 ) 
  
 { 
  
 // Link pending credential to account. 
  
 [[ 
 FIRAuth 
  
 auth 
 ]. 
 currentUser 
  
 linkWithCredential 
 : 
 pendingCred 
  
 completion 
 : 
 ^ 
 ( 
 FIRUser 
  
 * 
 _Nullable 
  
 user 
 , 
  
 NSError 
  
 * 
 _Nullable 
  
 error 
 ) 
  
 { 
  
 // ... 
  
 }]; 
  
 } 
  
 }]; 
  
 } 
  
 }]; 
  
 return 
 ; 
  
 } 
  
 // Other errors. 
  
 if 
  
 ( 
 error 
 ) 
  
 { 
  
 // handle the error. 
  
 return 
 ; 
  
 } 
  
 // Sign in with the credential. 
  
 if 
  
 ( 
 credential 
 ) 
  
 { 
  
 [[ 
 FIRAuth 
  
 auth 
 ] 
  
 signInAndRetrieveDataWithCredential 
 : 
 credential 
  
 completion 
 : 
 ^ 
 ( 
 FIRAuthDataResult 
  
 * 
 _Nullable 
  
 authResult 
 , 
  
 NSError 
  
 * 
 _Nullable 
  
 error 
 ) 
  
 { 
  
 if 
  
 ( 
 error 
 ) 
  
 { 
  
 // handle the error. 
  
 return 
 ; 
  
 } 
  
 }]; 
  
 } 
  
 }]; 
  

Next steps

After a user signs in for the first time, a new user account is created and linked to the credentials—that is, the user name and password, phone number, or auth provider information—the user signed in with. This new account is stored as part of your Firebase project, and can be used to identify a user across every app in your project, regardless of how the user signs in.

• In your apps, you can get the user's basic profile information from the User object. See Manage Users .

• In your Firebase Realtime Database and Cloud Storage Security Rules , you can get the signed-in user's unique user ID from the auth variable, and use it to control what data a user can access.

You can allow users to sign in to your app using multiple authentication providers by linking auth provider credentials to an existing user account.

To sign out a user, call signOut: .

 let 
  
 firebaseAuth 
  
 = 
  
 Auth 
 . 
 auth 
 () 
 do 
  
 { 
  
 try 
  
 firebaseAuth 
 . 
 signOut 
 () 
 } 
  
 catch 
  
 let 
  
 signOutError 
  
 as 
  
 NSError 
  
 { 
  
 print 
 ( 
 "Error signing out: %@" 
 , 
  
 signOutError 
 ) 
 } 

 NSError 
  
 * 
 signOutError 
 ; 
 BOOL 
  
 status 
  
 = 
  
 [[ 
 FIRAuth 
  
 auth 
 ] 
  
 signOut 
 : 
& signOutError 
 ]; 
 if 
  
 ( 
 ! 
 status 
 ) 
  
 { 
  
 NSLog 
 ( 
 @"Error signing out: %@" 
 , 
  
 signOutError 
 ); 
  
 return 
 ; 
 } 

You may also want to add error handling code for the full range of authentication errors. See Handle Errors .