Problem to recover UID from firebase Authentication?

Question

I am trying to create a collection in Firebase and for the document of this collection I would like to take the authentication UID of the user registration, the registration of the authentication is ok but does not create the collection follows the code below:

the Code communicating with Firebase

import 'dart:async';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:scoped_model/scoped_model.dart';
import 'package:flutter/material.dart';

class UserModel extends Model{

  FirebaseAuth _auth = FirebaseAuth.instance;

  FirebaseUser firebaseUser;
  Map<String, dynamic> userData = Map();

  bool isLoading = false;

  void signUp({@required Map<String, dynamic> userData, @required String pass, @required VoidCallback onSuccess, @required VoidCallback onFail}){
    isLoading = true;
    notifyListeners();

    _auth.createUserWithEmailAndPassword(
        email: userData["email"],
        password: pass
    ).then((user) async{
      AuthResult firebaseUser = user;

      await _saveUserData(userData);

      onSuccess();
      isLoading = false;
      notifyListeners();
    }).catchError((e) async{
      onFail();
      isLoading = false;
      notifyListeners();
      print("erro");
    });
  }

  void signIn() async{
    isLoading = true;
    notifyListeners();

    await Future.delayed(Duration(seconds: 3));

    isLoading = false;
    notifyListeners();
  }

  void recoverPass(){

  }

  Future<Null> _saveUserData(Map<String, dynamic> userData) async{
    this.userData = userData;
    print("teste $userData");
    await Firestore.instance.collection("users").document(firebaseUser.uid).setData(userData);
  }
}

the View Code of the Registration Form

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:loja_virtual/models/user_model.dart';
import 'package:scoped_model/scoped_model.dart';

class SignUpScreen extends StatefulWidget {
  @override
  _SignUpScreenState createState() => _SignUpScreenState();
}

class _SignUpScreenState extends State<SignUpScreen> {
  final _nameController = TextEditingController();
  final _emailController = TextEditingController();
  final _passController = TextEditingController();
  final _addressController = TextEditingController();

  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Criar Conta"),
          centerTitle: true,
        ),
        body: ScopedModelDescendant<UserModel>(
          builder: (context, child, model) {
            if (model.isLoading) {
              return Center(child: CircularProgressIndicator());
            } else {
              return Form(
                key: _formKey,
                child: ListView(
                  padding: EdgeInsets.all(16.0),
                  children: <Widget>[
                    TextFormField(
                      controller: _nameController,
                      decoration: InputDecoration(hintText: "Nome Completo"),
                      validator: (text) {
                        if (text.isEmpty) {
                          return "Nome Inválido!";
                        }
                      },
                    ),
                    SizedBox(height: 16.0),
                    TextFormField(
                      controller: _emailController,
                      decoration: InputDecoration(hintText: "E-mail"),
                      keyboardType: TextInputType.emailAddress,
                      validator: (text) {
                        if (text.isEmpty || !text.contains("@")) {
                          return "E-mail inválido!";
                        }
                      },
                    ),
                    SizedBox(height: 16.0),
                    TextFormField(
                      controller: _passController,
                      decoration: InputDecoration(hintText: "Senha"),
                      obscureText: true,
                      validator: (text) {
                        if (text.isEmpty || text.length < 6) {
                          return "Senha Inválida!";
                        }
                      },
                    ),
                    SizedBox(height: 16.0),
                    TextFormField(
                      controller: _addressController,
                      decoration: InputDecoration(hintText: "Endereço"),
                      validator: (text) {
                        if (text.isEmpty) {
                          return "Senha Inválido!";
                        }
                      },
                    ),
                    SizedBox(height: 16.0),
                    SizedBox(
                      height: 44.0,
                      child: RaisedButton(
                          child: Text(
                            "Criar Conta",
                            style: TextStyle(
                              fontSize: 18.0,
                            ),
                          ),
                          textColor: Colors.white,
                          color: Theme.of(context).primaryColor,
                          onPressed: () {
                            if (_formKey.currentState.validate()) {

                              Map<String, dynamic> userData = {
                                "name": _nameController.text,
                                "email": _emailController.text,
                                "address": _addressController.text
                              };

                              model.signUp(
                                  userData: userData,
                                  pass: _passController.text,
                                  onSuccess: _onSuccess,
                                  onFail: _onFail
                              );
                            }
                          }),
                    ),
                  ],
                ),
              );
            }
          },
        ));
  }

  void _onSuccess() {}

  void _onFail() {}
}

I analyzed that the problem is in the code below:

Firestore.instance.collection("users").document(firebaseUser.uid).setData(userData);

specifically in the firebaseUser.uid variable where printing on the screen returns me the error below:

E/flutter ( 916): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: Nosuchmethoderror: The getter 'uid' was called on null. E/flutter ( 916): Receiver: null E/flutter ( 916): Tried Calling: uid E/flutter ( 916): #0 Object.noSuchMethod (Dart:core-patch/object_patch.Dart:53:5)

someone can help me?

Answer 1

You are not loading the variable FirebaseUser firebaseUser, therefore the problem...

Create the following method

  Future<Void> currentUserUID() async {
    firebaseUser = await _firebaseAuth.currentUser();
  }

And before I call _saveUserData do

  void signUp({@required Map<String, dynamic> userData, @required String pass, @required VoidCallback onSuccess, @required VoidCallback onFail}){
    isLoading = true;
    notifyListeners();

    _auth.createUserWithEmailAndPassword(
        email: userData["email"],
        password: pass
    ).then((user) async{
      AuthResult firebaseUser = user;

      await currentUserUID();
      await _saveUserData(userData);

      onSuccess();
      isLoading = false;
      notifyListeners();
    }).catchError((e) async{
      onFail();
      isLoading = false;
      notifyListeners();
      print("erro");
    });
  }

This way your variable will receive the data needed to be used later.

If you want to take a look, in one of my sample projects I created a connection class with firebase, this one.