Summary - Firebase Auth

Combine signup, signin and authStateChanges to make an auth flow.

Auth flow

An auth flow combines registration, sign-in, and state listening. First a user is created with createUserWithEmailAndPassword, then signed in with signInWithEmailAndPassword. The authStateChanges stream catches every state change and updates the UI. For sign-out, signOut is called.

await auth.createUserWithEmailAndPassword(
  email: 'a@b.com', password: '123456');
final cred = await auth.signInWithEmailAndPassword(
  email: 'a@b.com', password: '123456');
print(cred.user.email);
await auth.signOut();

Exercise Write a complete auth flow

Get the auth instance. First register with createUserWithEmailAndPassword. Then sign in with signInWithEmailAndPassword and print the email. Finally call signOut and print 'yok' if currentUser is null.

Show example solution

class User {
  final String email;
  User(this.email);
}

class UserCredential {
  final User user;
  UserCredential(this.user);
}

class FirebaseAuth {
  static final FirebaseAuth instance = FirebaseAuth._();
  FirebaseAuth._();
  User? _user;
  User? get currentUser => _user;

  Future<UserCredential> createUserWithEmailAndPassword({
    required String email,
    required String password,
  }) async {
    _user = User(email);
    return UserCredential(_user!);
  }

  Future<UserCredential> signInWithEmailAndPassword({
    required String email,
    required String password,
  }) async {
    _user = User(email);
    return UserCredential(_user!);
  }

  Future<void> signOut() async {
    _user = null;
  }

  Stream<User?> authStateChanges() async* {
    yield _user;
  }
}

void main() async {
  final auth = FirebaseAuth.instance;
  await auth.createUserWithEmailAndPassword(
    email: 'a@b.com',
    password: '123456',
  );
  final cred = await auth.signInWithEmailAndPassword(
    email: 'a@b.com',
    password: '123456',
  );
  print(cred.user.email);
  await auth.signOut();
  print(auth.currentUser?.email ?? 'yok');
}

Test yourself

Which is used to continuously monitor the signed-in user?
- Listening to the authStateChanges stream
- Calling signOut
- Calling createUserWithEmailAndPassword
- Reading currentUser once
Show answer

Listening to the authStateChanges stream — The authStateChanges stream emits on every auth change, making it suitable for continuous monitoring; currentUser is a one-time read.
Close the session
```
await auth.____();
```
Show answer
```
await auth.signOut();
```
Auth flow parts

createUserWithEmailAndPassword

Registration
signInWithEmailAndPassword

Sign in
authStateChanges

State listening
signOut

Sign out

Next lesson: What is Firestore?

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