The non-nullable local variable 'result' must be assigned before it can be used

Question

I cannot find the solution to this problem. I am creating a sign up screen connected to firebase but it is giving me this error, "The non-nullable local variable 'result' must be assigned before it can be used. Try giving it an initializer expression, or ensure that it's assigned on every execution path."

The error is here. On the first and third line under result.

FirebaseFirestore.instance.collection("User").doc(result.user!.uid).set({
  "UserName": userName.text,
  "UserId": result.user!.uid,
  "UserEmail": email.text,
  "UserAddress": address.text,
  "UserGender": isMale == true ? "Male" : "Female",
  "UserNumber": phoneNumber.text,
});

This is the whole code

`import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:e_commerce_application/screens/homepage.dart';
import 'package:e_commerce_application/screens/login.dart';
import 'package:e_commerce_application/widgets/changescreen.dart';
import 'package:e_commerce_application/widgets/mybutton.dart';
import 'package:e_commerce_application/widgets/mytextformField.dart';
import 'package:e_commerce_application/widgets/passwordtextformfield.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class SignUp extends StatefulWidget {
  @override
  _SignUpState createState() => _SignUpState();
}

final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
String p =
    r'^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$';

RegExp regExp = new RegExp(p);
bool obserText = true;
final TextEditingController email = TextEditingController();
final TextEditingController userName = TextEditingController();
final TextEditingController phoneNumber = TextEditingController();
final TextEditingController password = TextEditingController();
final TextEditingController address = TextEditingController();

bool isMale = true;
bool isLoading = false;

class _SignUpState extends State<SignUp> {
  void submit() async {
    UserCredential result;
    try {
      setState(() {
        isLoading = true;
      });
      result = await FirebaseAuth.instance.createUserWithEmailAndPassword(
          email: email.text, password: password.text);
      print(result);
    } on PlatformException catch (error) {
      var message = "Please Check Your Internet Connection ";
      if (error.message != null) {
        message = error.message!;
      }
      _scaffoldKey.currentState!.showSnackBar(SnackBar(
        content: Text(message.toString()),
        duration: Duration(milliseconds: 600),
        backgroundColor: Theme.of(context).primaryColor,
      ));
      setState(() {
        isLoading = false;
      });
    } catch (error) {
      setState(() {
        isLoading = false;
      });
      _scaffoldKey.currentState!.showSnackBar(SnackBar(
        content: Text(error.toString()),
        duration: Duration(milliseconds: 600),
        backgroundColor: Theme.of(context).primaryColor,
      ));

      print(error);
    }
    FirebaseFirestore.instance.collection("User").doc(result.user!.uid).set({
      "UserName": userName.text,
      "UserId": result.user!.uid,
      "UserEmail": email.text,
      "UserAddress": address.text,
      "UserGender": isMale == true ? "Male" : "Female",
      "UserNumber": phoneNumber.text,
    });
    Navigator.of(context)
        .pushReplacement(MaterialPageRoute(builder: (ctx) => HomePage()));
    setState(() {
      isLoading = false;
    });
  }

  void vaildation() async {
    if (userName.text.isEmpty &&
        email.text.isEmpty &&
        password.text.isEmpty &&
        phoneNumber.text.isEmpty &&
        address.text.isEmpty) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("All Flied Are Empty"),
        ),
      );
    } else if (userName.text.length < 6) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Name Must Be 6 "),
        ),
      );
    } else if (email.text.isEmpty) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Email Is Empty"),
        ),
      );
    } else if (!regExp.hasMatch(email.text)) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Please Try Vaild Email"),
        ),
      );
    } else if (password.text.isEmpty) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Password Is Empty"),
        ),
      );
    } else if (password.text.length < 8) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Password  Is Too Short"),
        ),
      );
    } else if (phoneNumber.text.length < 11 || phoneNumber.text.length > 11) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Phone Number Must Be 11 "),
        ),
      );
    } else if (address.text.isEmpty) {
      _scaffoldKey.currentState!.showSnackBar(
        SnackBar(
          content: Text("Address Is Empty "),
        ),
      );
    } else {
      submit();
    }
  }

  Widget _buildAllTextFormField() {
    return Container(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
          MyTextFormField(
            name: "UserName",
            controller: userName,
          ),
          SizedBox(
            height: 10,
          ),
          MyTextFormField(
            name: "Email",
            controller: email,
          ),
          SizedBox(
            height: 10,
          ),
          PasswordTextFormField(
            obserText: obserText,
            controller: password,
            name: "Password",
            onTap: () {
              FocusScope.of(context).unfocus();
              setState(() {
                obserText = !obserText;
              });
            },
          ),
          SizedBox(
            height: 10,
          ),
          GestureDetector(
            onTap: () {
              setState(() {
                isMale = !isMale;
              });
            },
            child: Container(
              height: 60,
              padding: EdgeInsets.only(left: 10),
              width: double.infinity,
              decoration: BoxDecoration(border: Border.all(color: Colors.grey)),
              child: Center(
                child: Row(
                  children: [
                    Text(
                      isMale == true ? "Male" : "Female",
                      style: TextStyle(color: Colors.black87, fontSize: 18),
                    ),
                  ],
                ),
              ),
            ),
          ),
          SizedBox(
            height: 10,
          ),
          MyTextFormField(
            name: "Phone Number",
            controller: phoneNumber,
          ),
          SizedBox(
            height: 10,
          ),
          MyTextFormField(
            name: "Address",
            controller: address,
          ),
        ],
      ),
    );
  }

  Widget _buildBottomPart() {
    return Container(
      margin: EdgeInsets.symmetric(horizontal: 10),
      width: double.infinity,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
          _buildAllTextFormField(),
          SizedBox(
            height: 10,
          ),
          isLoading == false
              ? MyButton(
            name: "SignUp",
            onPressed: () {
              vaildation();
            },
          )
              : Center(
            child: CircularProgressIndicator(),
          ),
          ChangeScreen(
            name: "Login",
            whichAccount: "I Have Already An Account!",
            onTap: () {
              Navigator.of(context).pushReplacement(
                MaterialPageRoute(
                  builder: (ctx) => Login(),
                ),
              );
            },
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      body: ListView(
        children: [
          Container(
            height: 200,

            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(
                  "Register",
                  style: TextStyle(
                    fontSize: 40,
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ],
            ),
          ),
          Container(
            height: 500,
            child: _buildBottomPart(),
          ),
        ],
      ),
    );
  }
}
`

score 0 · Answer 1 · answered Aug 23 '21 at 06:51

You are assigning result in your try catch, and accessing it after your try catch.

So if anything happens in your try block, result will never be assigned, and you cannot access whatever you want on it.

Solution would be to put your Firestore Call in your try catch block.

 try {
  setState(() {
    isLoading = true;
  });
  result = await FirebaseAuth.instance.createUserWithEmailAndPassword(
      email: email.text, password: password.text);
  print(result);
  FirebaseFirestore.instance.collection("User").doc(result.user!.uid).set({
    "UserName": userName.text,
    "UserId": result.user!.uid,
    "UserEmail": email.text,
    "UserAddress": address.text,
    "UserGender": isMale == true ? "Male" : "Female",
    "UserNumber": phoneNumber.text,
  });

score 0 · Answer 2 · answered Dec 26 '21 at 02:44

Null safety in dart also cause this error in my code. The only solution is to assign a pre-define value to variable.

    String imagePath = "path";
    String imageName = '/image.jpeg';

I was getting this error in last line, in var imagePath.

class _newpostState extends State<newpost> {
//class newpost extends StatefulWidget {
  //const newpost({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    String imagePath = "path";
    String imageName = '/image.jpeg';
    void pickImage() async {
      final ImagePicker _picker = ImagePicker();
      final XFile? image = await _picker.pickImage(source: ImageSource.gallery);
      print(image!.name);
      setState(() {
        imagePath = image.path;
        imageName = image.name;
      });
    }

    final TextEditingController titlecontroller = TextEditingController();
    final TextEditingController DcripController = TextEditingController();
    final TextEditingController passwordController = TextEditingController();
    void submit() async {
      //for post database

      FirebaseAuth auth = FirebaseAuth.instance;
      FirebaseFirestore firestore = FirebaseFirestore.instance;
      //for storage
      firebase_storage.FirebaseStorage storage =
          firebase_storage.FirebaseStorage.instance;

      try {
        File file = File(imagePath);
        await storage.ref(imageName).putFile(file);

score 0 · Answer 3 · answered Sep 24 '22 at 21:01

It's so, frustrating to read "variable must be assigned before it can be used" because you already assigned the variable. to solve this issue, provide a default value when you create the variable. suppose the variable is a string.

String result;  // instead of this

String result= ""; // use this

The non-nullable local variable 'result' must be assigned before it can be used

3 Answers3