signInWithEmailAndPassword

Flutter course
Advanced
Lesson 18/69
4 min

signInWithEmailAndPassword

The signInWithEmailAndPassword method signs in a registered user. If the email and password are correct, it returns a UserCredential and currentUser is updated. If the password is wrong, a FirebaseAuthException is thrown.

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

The signOut method

The signOut method closes the session and currentUser becomes null. You call this method when the user leaves the app or wants to switch to another account. The call is asynchronous, so you await it with await.

await auth.signOut();
print(auth.currentUser); // null

Practice Sign in and sign out

Get the auth instance, sign in with signInWithEmailAndPassword, print the email. Then call signOut, check currentUser and print 'yok' if it is null.

Starter code

main.dart

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

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

void main() async {
  // giriş metodunu çağır, e-postayı yazdır
  // çıkış metodunu çağır, 'yok' yazdır
}

Sample solution

main.dart

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

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

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

Expected output

a@b.com
yok

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What happens when signInWithEmailAndPassword is given a wrong password?

The app closes
An empty UserCredential is returned
null is returned
A FirebaseAuthException is thrown Correct answer

Explanation: When the password is wrong, a FirebaseAuthException is thrown; it does not return null or an empty UserCredential.

2 Call the sign-in method

Question

final cred = await auth.____(
  email: 'a@b.com',
  password: '123456',
);

Answer

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

Explanation: To sign in you call signInWithEmailAndPassword; the email and password parameters are required.

3 Sign-in and sign-out parts

Term	Meaning
`signInWithEmailAndPassword`	Signs in
`signOut`	Signs out
`UserCredential`	Sign-in result
`currentUser`	Current user

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> signInWithEmailAndPassword({ required String email, required String password, }) async { _user = User(email); return UserCredential(_user!); } Future<void> signOut() async { _user = null; } } void main() async { final auth = FirebaseAuth.instance; final cred = await auth.signInWithEmailAndPassword( email: 'a@b.com', password: '123456', ); print(cred.user.email); await auth.signOut(); print(auth.currentUser?.email ?? 'yok'); }

All lessons in Advanced

signInWithEmailAndPassword