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.
- In Xcode, with your app project open, navigate to
File > Add Packages
.
- When prompted, add the Firebase Apple platforms SDK repository:
https://github.com/firebase/firebase-ios-sdk.git
- Choose the Firebase Authentication library.
- Add the
-ObjC
flag to the
Other Linker Flags
section of your target's build settings.
-
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:
Add Firebase to your Apple project
.
Include the following pods in your
Podfile
:
pod 'FirebaseAuth'
- In the
Firebase console
, open the
Auth
section.
- On the
Sign in method
tab, enable the
Twitter
provider.
- Add the
API key
and
API secret
from that provider's developer console to the
provider configuration:
- Register your app
as a developer application on Twitter and get your app's OAuth
API key
and
API secret
.
- 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
.
- 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:
Add custom URL schemes to your Xcode project:
- 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.
- 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):
Create an instance of an
OAuthProvider
using the provider ID
twitter.com
.
Swift
var provider = OAuthProvider(providerID: "twitter.com")
Objective-C
FIROAuthProvider *provider = [FIROAuthProvider providerWithProviderID:@"twitter.com"];
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
,
scope
and
state
.
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
.
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
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
}];
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
}];
Handling account-exists-with-different-credential Errors
If you enabled the
One account per email address
setting in the
Firebase console
,
when a user tries to sign in a to a provider (such as Twitter) with an email that already
exists for another Firebase user's provider (such as Google), the error
FIRAuthErrorCodeAccountExistsWithDifferentCredential
is thrown along with a temporary
FIRAuthCredential
object (Twitter credential). To complete the sign in to the
intended provider, the user has to sign first to the existing provider (Google) and then link to the
former
FIRAuthCredential
(Twitter credential). This would look as illustrated below:
Swift
// 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
}
}
}
}
Objective-C
// 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:
.
Swift
let firebaseAuth = Auth.auth()
do {
try firebaseAuth.signOut()
} catch let signOutError as NSError {
print("Error signing out: %@", signOutError)
}
Objective-C
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
.