Get Started with Firebase Authentication on Apple Platforms

You can use Firebase Authentication to allow users to sign in to your app using one or more sign-in methods, including email address and password sign-in, and federated identity providers such as Google Sign-in and Facebook Login. This tutorial gets you started with Firebase Authentication by showing you how to add email address and password sign-in to your app.

Connect your app to Firebase

1. Install the Firebase SDK.
2. In the Firebase console, add your app to your Firebase project.

Add Firebase Authentication to your app

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.

(Optional) Prototype and test with Firebase Local Emulator Suite

Before talking about how your app authenticates users, let's introduce a set of tools you can use to prototype and test Authentication functionality: Firebase Local Emulator Suite. If you're deciding among authentication techniques and providers, trying out different data models with public and private data using Authentication and Firebase Security Rules, or prototyping sign-in UI designs, being able to work locally without deploying live services can be a great idea.

An Authentication emulator is part of the Local Emulator Suite, which enables your app to interact with emulated database content and config, as well as optionally your emulated project resources (functions, other databases, and security rules).

Using the Authentication emulator involves just a few steps:

1. Adding a line of code to your app's test config to connect to the emulator.
2. From the root of your local project directory, running firebase emulators:start.
3. Using the Local Emulator Suite UI for interactive prototyping, or the Authentication emulator REST API for non-interactive testing.

A detailed guide is available at Connect your app to the Authentication emulator. For more information, see the Local Emulator Suite introduction.

Now let's continue with how to authenticate users.

Initialize the Firebase SDK

In your app delegate, first import the Firebase SDK:

import FirebaseCore
AppDelegate.swift

@import FirebaseCore;
AppDelegate.m

Then, in the application:didFinishLaunchingWithOptions: method, initialize the FirebaseApp object:

// Use Firebase library to configure APIs
FirebaseApp.configure()
AppDelegate.swift

// Use Firebase library to configure APIs
[FIRApp configure];
AppDelegate.m

Listen for authentication state

For each of your app's views that need information about the signed-in user, attach a listener to the FIRAuth object. This listener gets called whenever the user's sign-in state changes.

Attach the listener in the view controller's viewWillAppear method:

handle = Auth.auth().addStateDidChangeListener { auth, user in
  // ...
}
MainViewController.swift

self.handle = [[FIRAuth auth]
    addAuthStateDidChangeListener:^(FIRAuth *_Nonnull auth, FIRUser *_Nullable user) {
      // ...
    }];
MainViewController.m

And detach the listener in the view controller's viewWillDisappear method:

Auth.auth().removeStateDidChangeListener(handle!)
MainViewController.swift

[[FIRAuth auth] removeAuthStateDidChangeListener:_handle];
MainViewController.m

Sign up new users

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

Auth.auth().createUser(withEmail: email, password: password) { authResult, error in
  // ...
}
EmailViewController.swift

[[FIRAuth auth] createUserWithEmail:email
                           password:password
                         completion:^(FIRAuthDataResult * _Nullable authResult,
                                      NSError * _Nullable error) {
  // ...
}];
EmailViewController.m

Sign in existing users

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

Auth.auth().signIn(withEmail: email, password: password) { [weak self] authResult, error in
  guard let strongSelf = self else { return }
  // ...
}
EmailViewController.swift

[[FIRAuth auth] signInWithEmail:self->_emailField.text
                       password:self->_passwordField.text
                     completion:^(FIRAuthDataResult * _Nullable authResult,
                                  NSError * _Nullable error) {
  // ...
}];
EmailViewController.m

Get user information

After a user signs in successfully, you can get information about the user. For example, in your authentication state listener:

if let user = user {
  // 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 getTokenWithCompletion:completion: instead.
  let uid = user.uid
  let email = user.email
  let photoURL = user.photoURL
  var multiFactorString = "MultiFactor: "
  for info in user.multiFactor.enrolledFactors {
    multiFactorString += info.displayName ?? "[DispayName]"
    multiFactorString += " "
  }
  // ...
}
MainViewController.swift

if (user) {
  // 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 getTokenWithCompletion:completion: instead.
  NSString *email = user.email;
  NSString *uid = user.uid;
  NSMutableString *multiFactorString = [NSMutableString stringWithFormat:@"MultiFactor: "];
  for (FIRMultiFactorInfo *info in user.multiFactor.enrolledFactors) {
    [multiFactorString appendString:info.displayName];
    [multiFactorString appendString:@" "];
  }
  NSURL *photoURL = user.photoURL;
  // ...
}
MainViewController.m

Next steps

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

• Google Sign-in
• Facebook Login
• Twitter Login
• GitHub Login
• Anonymous sign-in