Wait for an asynchronous function to finish to continue

Question

I can expect an asynchronous terminal function to continue the code?

I have an asynchronous function with a Try/catch and want to catch the bug to treat.

Login(BuildContext context) async { 
try {
      FirebaseUser _login = (await FirebaseAuth.instance
              .signInWithEmailAndPassword(email: email, password: pass))
          .user;

      if (_login != null) {
        userid = _user.uid;
        Modular.to.pushNamed('/inicial');
      }
    } catch (e) {
      msge = e.code;
    }
  }

When I call the function and try to get the msge it returns null, I did some tests and from what I understand it returns null because it has not yet finished.

Is there any way to take this data?

Answer 1

Just remembering, the functions should always start with lowercase letters (Lower-case).

Regarding your problem, I believe you’re trying to capture the user before function signInWithEmailAndPassword return something, so trying to access the value of a null variable will cause another error other than firebase validation.

Try to modify your function as follows:

  void login(BuildContext context) async { 
    final FirebaseAuth firebaseAuth = FirebaseAuth.instance;

    try {
      await firebaseAuth.signInWithEmailAndPassword(email: email, password: password);
      FirebaseUser user = await firebaseAuth.currentUser();

      if (user != null) {
        userid = user.uid;
        Modular.to.pushNamed('/inicial');
      }
    } catch (e) {
      msge = e.code;
    }
  }

Your property msge will only receive a value if the signInWithEmailAndPassword() returns some of the pre-defined errors in the package.

Explaining

The await causes the application to wait for the asynchronous call to end so that the execution of that function block continues.

So if you’re using the property msge in another place, most likely it is being returned NULL because there is no time to be fed by the method login.