You can useFirebase Authentication to allow users to sign in to your app using oneor more sign-in methods, including email address and password sign-in, andfederated identity providers such as Google Sign-in and Facebook Login. Thistutorial gets you started withFirebase Authentication by showing you how to addemail address and password sign-in to your app.

Connect your C++ project to Firebase

Before you can useFirebase Authentication,you need to:

• Register your C++ project and configure it to use Firebase.

  If your C++ project already uses Firebase, then it's already registered andconfigured for Firebase.

• Add theFirebaseC++ SDK to your C++ project.

Note that adding Firebase to your C++ project involves tasks both in theFirebase console and in your open C++ project (for example, you downloadFirebase config files from the console, then move them into your C++ project).

Sign up new users

Create a form that allows new users to register with your app using theiremail address and a password. When a user completes the form, validate theemail address and password provided by the user, then pass them to theCreateUserWithEmailAndPassword method:

firebase::Future<firebase::auth::AuthResult>result=auth->CreateUserWithEmailAndPassword(email,password);

You can check the status of the account creation operation either by registeringa callback on theCreateUserWithEmailAndPasswordLastResult Future object, or,if you're writing a game or app with some kind of periodic update loop, bypolling the status in the update loop.

For example, using a 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::AuthResult>&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);

Or, to use polling, do something like the following example in your game'supdate loop:

firebase::Future<firebase::auth::AuthResult>result=auth->CreateUserWithEmailAndPasswordLastResult();if(result.status()==firebase::kFutureStatusComplete){if(result.error()==firebase::auth::kAuthErrorNone){firebase::auth::AuthResult*auth_result=*result.result();printf("Create user succeeded for email %s\n",auth_result.user.email().c_str());}else{printf("Created user failed with error '%s'\n",result.error_message());}}

Sign in existing users

Create a form that allows existing users to sign in using their email addressand password. When a user completes the form, call theSignInWithEmailAndPassword method:

firebase::Future<firebase::auth::AuthResult>result=auth->SignInWithEmailAndPassword(email,password);

Get the result of the sign-in operation the same way you got the sign-up result.

Set an authentication state listener and get account data

To respond to sign-in and sign-out events, attach a listener to the globalauthentication object. This listener gets called whenever the user's sign-instate changes. Because the listener runs only after the authentication object isfully initialized and after any network calls have completed, it is the bestplace to get information about the signed-in user.

Create the listener by implementing thefirebase::auth::AuthStateListenerabstract class. For example, to create a listener that gets information aboutthe user when a user successfully signs in:

classMyAuthStateListener:publicfirebase::auth::AuthStateListener{public:voidOnAuthStateChanged(firebase::auth::Auth*auth)override{firebase::auth::Useruser=auth.current_user();if(user.is_valid()){// User is signed inprintf("OnAuthStateChanged: signed_in %s\n",user.uid().c_str());conststd::stringdisplayName=user.DisplayName();conststd::stringemailAddress=user.Email();conststd::stringphotoUrl=user.PhotoUrl();}else{// User is signed outprintf("OnAuthStateChanged: signed_out\n");}// ...}};

Attach the listener with thefirebase::auth::Auth object'sAddAuthStateListener method:

MyAuthStateListenerstate_change_listener;auth->AddAuthStateListener(&state_change_listener);

Next steps

Learn how to add support for other identity providers and anonymous guestaccounts:

• Google Sign-in
• Facebook Login
• Apple Login
• Twitter Login
• GitHub Login
• Microsoft Login
• Yahoo Login
• Anonymous sign-in
• Phone Authentication