CODEWITHSUNDEEP
firebaseflutterdartfirebase-authenticationuid
cabral279
cabral279

Reputation: 97

Flutter/Dart How to transform user uid from firebase in a variable?

I am trying to take the uid from Firebase and put it in a variable, to use it in another class, but the maximum I made until now is display the value in the homepage as a text. When I try to create final String riderId = snapshot.data.uid; in the homepage, it prints the error:

The getter 'uid' was called on null. Receiver: null Tried calling: uid

I already saw other questions in stackoverflow and tutorials on youtube, but none of them worked for me!

My homepage:

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // print(riderId);
    return StreamBuilder(
      stream: AuthenticationService().authStateChanges,
      builder: (BuildContext context, AsyncSnapshot<User> snapshot) {
        // final String riderId = snapshot.data.uid;
        if (snapshot.hasData) {
          return Center(
            child: Text(snapshot.data.uid),
          );
        } else {
          return Text('Loading...');
        },},);}}

My signIn button

RaisedButton(
              onPressed: () {
                context.read<AuthenticationService>().signIn(
                      email: emailController.text.trim(),
                      password: passwordController.text.trim(),
                    );
              },
              child: Text("Sign in"),
            ),

My main.dart

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        Provider<AuthenticationService>(
          create: (_) => AuthenticationService(),
        ),
        StreamProvider(
          create: (context) =>
              context.read<AuthenticationService>().authStateChanges,
        )
      ],
      child: MaterialApp(...

My authentication service page

class AuthenticationService {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;

  Stream<User> get authStateChanges => _firebaseAuth.idTokenChanges();

  
  Future<UserModel> signIn({String email, String password}) async {
   
      var result = await _firebaseAuth.signInWithEmailAndPassword(
          email: email, password: password);
      return UserModel(result.user.uid);
    } 
  }

Upvotes: 1

Views: 479

Answers (2)

osaxma
osaxma

Reputation: 3014

The stream can emit null as a first event. So you should always access the uid after you do a null check or check if snapshot.hasData:

  
  @override
  Widget build(BuildContext context) {
    // print(riderId);
    return StreamBuilder(
      stream: AuthenticationService().authStateChanges,
      builder: (BuildContext context, AsyncSnapshot<User> snapshot) {
        // final String riderId = snapshot.data.uid; // <~~ you'll always get an error in the first event if it's null
        if (snapshot.hasData) {
          final String riderId = snapshot.data.uid; // <~~ here should be fine
          return Center(
            child: Text(snapshot.data.uid),
          );
        } else {
          return Text('Loading...');
        },},);}}

Upvotes: 1

Sal Man
Sal Man

Reputation: 147

Try to use authStateChanges()

 Stream<User> get authStateChanges => FirebaseAuth.instance.authStateChanges();

or

Stream<User> get authStateChanges => FirebaseAuth.instance.userChanges();

Upvotes: 1

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