Sistema de SMS Auth com firebase

sms_firebase_auth.dart

import 'package:firebase_auth/firebase_auth.dart';

class SMSFunctions {
  
  static Future<void> sendCodeToPhoneNumber(
    String phoneNo,
    Function onSuccess,
    Function onFailed,
    Function onRetrival,
  ) async {
    FirebaseAuth.instance.signOut();
    
    // Verifica  Celular
    final PhoneVerificationCompleted verificationCompleted =
        (AuthCredential user) {
      onRetrival();
    };
    
    // Falhou ao verificar o celular
    final PhoneVerificationFailed verificationFailed =
        (FirebaseAuthException authException) {
      onFailed();
    };
    
    // Enviar codigo para o celular
    final PhoneCodeSent codeSent =
        (String verificationId, [int forceResendingToken]) async {
      verificationId = verificationId;
      onSuccess(verificationId);
    };
    
    // Pegar automaticamente o código enviado
    final PhoneCodeAutoRetrievalTimeout codeAutoRetrievalTimeout =
        (String verificationId) {
      verificationId = verificationId;
      onFailed();
    };
    
    await FirebaseAuth.instance.verifyPhoneNumber(
        phoneNumber: phoneNo,
        timeout: const Duration(seconds: 5),
        verificationCompleted: verificationCompleted,
        verificationFailed: verificationFailed,
        codeSent: codeSent,
        codeAutoRetrievalTimeout: codeAutoRetrievalTimeout);
  }

  static Future<bool> confirmSMS(String smsCode, String verificationId) async {
    final AuthCredential credential = PhoneAuthProvider.credential(
      verificationId: verificationId,
      smsCode: smsCode,
    );
    UserCredential authResult;
    try {
      authResult = await FirebaseAuth.instance.signInWithCredential(credential);
      final User currentUser = authResult.user;
      if (currentUser != null)
        return true;
      else
        return false;
    } catch (e) {}
    return false;
  }
}