Check if user exists on FIrestore - firebase

Question

I have this function that use SignInWithGogle to Sign In/Up an user
void _signInWithGoogle() async {
final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
final GoogleSignInAuthentication googleAuth =
await googleUser.authentication;
final AuthCredential credential = GoogleAuthProvider.getCredential(
accessToken: googleAuth.accessToken,
idToken: googleAuth.idToken,
);
final FirebaseUser user = (await _auth.signInWithCredential(credential)).user;
assert(user.email != null);
assert(user.displayName != null);
assert(!user.isAnonymous);
assert(await user.getIdToken() != null);
final FirebaseUser currentUser = await _auth.currentUser();
assert(user.uid == currentUser.uid);
print('user email here $user.email');
setState(() {
if (user != null) {
_success = true;
_userID = user.uid;
final userToSubmit = User(
email: user.email,
id: user.uid,
name: user.displayName,
owner: false,
favorites: null);
print('USER ID USER ID USER ID ${user.uid}');
DocumentReference dbRef =
Firestore.instance.collection('users').document(user.uid);
dbRef.get().then((value) {
print('VALUE EXISTS? ${value.exists} y VALUE $value');
value.exists ?
_goToHomeScreen(user)
:
dbRef
.collection('prf')
.document('profile')
.setData(userToSubmit.toJson())
.then(_goToHomeScreen(user));
});
} else {
_success = false;
}
});
}
The problem is that when the user logOut and then login it sets the new Data and the user lost everything they have like favorites and so on... I thought that checking if the document exists should resolve the problem, but despite the document is there exists returns false.
This is the piece of code I'm talking about
DocumentReference dbRef =
Firestore.instance.collection('users').document(user.uid);
dbRef.get().then((value) {
print('VALUE EXISTS? ${value.exists} y VALUE $value');
value.exists ?
_goToHomeScreen(user)
:
dbRef
.collection('prf')
.document('profile')
.setData(userToSubmit.toJson())
.then(_goToHomeScreen(user));
});
}
Why it returns false even if the user.uid and the document exists? What am I doing wrong?

Answer 1

The final solution I implemented is this:
FirebaseUser firebaseUser;
try {
firebaseUser = (await FirebaseAuth.instance.signInWithCredential(credential)).user;
} catch(e) {
print(e.toString());
} finally {
final userToSubmit = User(
email: firebaseUser.email,
id: firebaseUser.uid,
name: firebaseUser.displayName,
owner: false,
restauranteAdded: false);
DocumentReference dbRef =
Firestore.instance.collection('users').document(firebaseUser.uid).collection('nameOfTheCollection').document('documentName');
dbRef.get().then((data) {
data.exists ? _goToHomeScreen(user) :
_createUser();
});
This way I check if user document exists in my Firestore Database and if not it creates it.

Answer 2

There is a lot going on. In general, you're not updating any state object with the setState() method. setState is used to tell a widget that some state has changed--and it's called synchronously with the change, but here where you're just checking to see if a document exists and nothing is changing, it's not needed.
Also it doesn't appear that you're actually returning a user object at all, so this code as I read it will always return false.
You should remove setState here altogether (not needed for what you're doing)
Run a sign in method that returns the user object you want do do things with.
Access your db once you know you have a signed in user (i.e. w/ uid of signed in user)
Here is an option to try:
//Create a User class so that you don't have to call FireBase in your methods.
class User {
User({
#required this.uid,
this.email,
this.displayName,
});
final String uid;
final String email;//these are whatever you want
final String displayName;
}
//put sign in methods into an abstract class. Don't have to, but keeps code flexible if you don't stay with firebase
abstract class AuthBase {
//add in other signin methods as needed
Future<User> signInWithGoogle();
}
//Implement AuthBase in class Auth
class Auth implements AuthBase {
final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
//Get a User from Firebase User
User _userFromFirebase(FirebaseUser user) {
if (user == null) {
return null;
}
return User(
uid: user.uid,
displayName: user.displayName,
email: user.email,
);
}
//your signinWithGoogle method
Future<User> signInWithGoogle() async {
//where User is the class you've created
GoogleSignIn googleSignIn = GoogleSignIn();
GoogleSignInAccount googleUser = await googleSignIn.signIn();
if (googleUser != null) {
GoogleSignInAuthentication googleAuth = await googleUser.authentication;
if (googleAuth.idToken != null && googleAuth.accessToken != null) {
final authResult = await _firebaseAuth.signInWithCredential( //await your instance of FirebaseAuth
GoogleAuthProvider.getCredential(
idToken: googleAuth.idToken,
accessToken: googleAuth.accessToken,
),
);
return _userFromFirebase(authResult.user); //your signed in firebase user that you can do stuff with uid, email, displayname, etc.
} else {
throw PlatformException(
code: 'ERROR_MISSING_GOOGLE_AUTH_TOKEN',
message: '',
);
}
} else {
throw PlatformException(
code: 'ERROR_ABORTED_BY_USER',
message: '',
);
}
}