You can let your users authenticate with Firebase using their GitHub accountsby integrating GitHub authentication into your app.

Before you begin

1. Add Firebase to your C++ project.
2. In theFirebase console, open theAuth section.
3. On theSign in method tab, enable theGitHub provider.
4. Add theClient ID andClient Secret from that provider's developer console to the provider configuration:
   1. Register your app as a developer application on GitHub and get your app's OAuth 2.0Client ID andClient Secret.
   2. Make sure your FirebaseOAuth redirect URI (e.g.my-app-12345.firebaseapp.com/__/auth/handler) is set as yourAuthorization callback URL in your app's settings page on yourGitHub app's config.
5. ClickSave.

Access thefirebase::auth::Auth class

1. Add the Auth and App header files:

   #include"firebase/app.h"#include"firebase/auth.h"

2. In your initialization code, create afirebase::App class.

   #if defined(__ANDROID__)firebase::App*app=firebase::App::Create(firebase::AppOptions(),my_jni_env,my_activity);#elsefirebase::App*app=firebase::App::Create(firebase::AppOptions());#endif// defined(__ANDROID__)

3. Acquire thefirebase::auth::Auth class for yourfirebase::App.There is a one-to-one mapping betweenApp andAuth.

   firebase::auth::Auth*auth=firebase::auth::Auth::GetAuth(app);

Authenticate with Firebase

1. Follow instructions forAndroid andiOS+ to get a token for the signed-in GitHub user.
2. After a user successfully signs in, exchange the token for a Firebase credential, and authenticate with Firebase using the Firebase credential:

   firebase::auth::Credentialcredential=firebase::auth::GitHubAuthProvider::GetCredential(token);firebase::Future<firebase::auth::AuthResult>result=auth->SignInAndRetrieveDataWithCredential(credential);

3. If your program has an update loop that runs regularly (say at 30 or 60 times per second), you can check the results once per update withAuth::SignInAndRetrieveDataWithCredentialLastResult:

   firebase::Future<firebase::auth::AuthResult>result=auth->SignInAndRetrieveDataWithCredentialLastResult();if(result.status()==firebase::kFutureStatusComplete){if(result.error()==firebase::auth::kAuthErrorNone){firebase::auth::AuthResultauth_result=*result.result();printf("Sign in succeeded for `%s`\n",auth_result.user.display_name().c_str());}else{printf("Sign in failed with error '%s'\n",result.error_message());}}

   Or, if your program is event driven, you may prefer toregister a callback on the Future.

Register a callback on a Future

voidOnCreateCallback(constfirebase::Future<firebase::auth::User*>&result,void*user_data){// The callback is called when the Future enters the `complete` state.assert(result.status()==firebase::kFutureStatusComplete);// Use `user_data` to pass-in program context, if you like.MyProgramContext*program_context=static_cast<MyProgramContext*>(user_data);// Important to handle both success and failure situations.if(result.error()==firebase::auth::kAuthErrorNone){firebase::auth::User*user=*result.result();printf("Create user succeeded for email %s\n",user->email().c_str());// Perform other actions on User, if you like.firebase::auth::User::UserProfileprofile;profile.display_name=program_context->display_name;user->UpdateUserProfile(profile);}else{printf("Created user failed with error '%s'\n",result.error_message());}}voidCreateUser(firebase::auth::Auth*auth){// Callbacks work the same for any firebase::Future.firebase::Future<firebase::auth::AuthResult>result=auth->CreateUserWithEmailAndPasswordLastResult();// `&my_program_context` is passed verbatim to OnCreateCallback().result.OnCompletion(OnCreateCallback,&my_program_context);}

voidCreateUserUsingLambda(firebase::auth::Auth*auth){// Callbacks work the same for any firebase::Future.firebase::Future<firebase::auth::AuthResult>result=auth->CreateUserWithEmailAndPasswordLastResult();// The lambda has the same signature as the callback function.result.OnCompletion([](constfirebase::Future<firebase::auth::User*>&result,void*user_data){// `user_data` is the same as &my_program_context, below.// Note that we can't capture this value in the [] because std::function// is not supported by our minimum compiler spec (which is pre C++11).MyProgramContext*program_context=static_cast<MyProgramContext*>(user_data);// Process create user result...(void)program_context;},&my_program_context);}

Next steps

After a user signs in for the first time, a new user account is created andlinked to the credentials—that is, the user name and password, phonenumber, or auth provider information—the user signed in with. This newaccount is stored as part of your Firebase project, and can be used to identifya 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 thefirebase::auth::User object:

  firebase::auth::Useruser=auth->current_user();if(user.is_valid()){std::stringname=user.display_name();std::stringemail=user.email();std::stringphoto_url=user.photo_url();// The user's ID, unique to the Firebase project.// Do NOT use this value to authenticate with your backend server,// if you have one. Use firebase::auth::User::Token() instead.std::stringuid=user.uid();}

• In yourFirebase Realtime Database andCloud StorageSecurity Rules, you can get the signed-in user's unique user ID from theauth variable, and use it to control what data a user can access.

You can allow users to sign in to your app using multiple authenticationproviders bylinking auth provider credentials to anexisting user account.

To sign out a user, callSignOut():

auth->SignOut();