How can I return two string values in dart flutter

Question

I am working on my flutter project where I want to use sharedpreferences. Look at the code below:

Future<String?> getCredentials() async {
   final localStorage = await SharedPreferences.getInstance();
   final email = localStorage.getString('email');
   final password = localStorage.getString('password');
   return email, password;
}

This is my getCredentials funtion I want this function to return email and password as different parameters but dart doesn't allow me can you please help me How can I do it?

Whole SharedPreference Code:

import 'package:shared_preferences/shared_preferences.dart';

class sharedPreference {
  Future<String?> saveCredentials({
    required String email,
    required String password,
  }) async {
    final localStorage = await SharedPreferences.getInstance();
    await localStorage.setString('email', email);
    await localStorage.setString('password', password);
  }

  Future<String?> getCredentials() async {
    final localStorage = await SharedPreferences.getInstance();
    final email = localStorage.getString('email');
    final password = localStorage.getString('password');
    return email, password;
  }
}

@Patrick Is there any other way If i can't store passsword but still user can login without credentials if they logged in once? — Mr Fin
– Mr Fin, Commented Nov 16, 2022 at 12:45
Store only a password hash, for example with the crypto package. — Patrick
– Patrick, Commented Nov 16, 2022 at 13:10

LacticWhale · Accepted Answer · 2022-11-16 22:16:06Z

3

Just create class. You can even add methods to Credentials later. Like secure compare to compare passwordHash with constant time.

class Credentials {
  Credentials(this.email, this.passwordHash);

  final String email;
  final String passwordHash;
}

Future<Credentials> getCredentials() async {
   final localStorage = await SharedPreferences.getInstance();
   final email = localStorage.getString('email');
   final passwordHash = localStorage.getString('passwordHash');
   return Credentials(email, passwordHash));
}

Edit use crypto to get hash of password:

import 'dart:convert';
import 'package:crypto/crypto.dart';

String getHash(String plainPassword) {
    return sha256.convert(utf8.encode(plainPassword)).toString();
}

edited Nov 16, 2022 at 22:16

answered Nov 16, 2022 at 11:03

LacticWhale

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Comments

Irfan Ganatra · Accepted Answer · 2022-11-16 10:52:15Z

0

change return type String to Map<String,dynamic>

Future<Map<String,dynamic>> getCredentials() async {
   final localStorage = await SharedPreferences.getInstance();
   final email = localStorage.getString('email');
   final password = localStorage.getString('password');
   return {
'email':email,
'password':password

};
}

answered Nov 16, 2022 at 10:52

Irfan Ganatra

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4 Comments

Irfan Ganatra Over a year ago

and there is a advise not to store password...but if u want..u may set return type to Map<String,dynamic>

LacticWhale Over a year ago

tbh, you should create class with fields email and password and return it for better readability (and intellisense).

Mr Fin Over a year ago

@IrfanGanatra Is there any other way If i can't store passsword but still user can login without credentials if they logged in once?

LacticWhale Over a year ago

@MrFin you only need to store hash of password. Use crypto to hash it in store in database or whatever. And then user tries to logging you can hash his input and compare it to stored value. This will ensure that even if database get leaked you won't expose passwords in plain text. Also plz for the god sake use my answer. Ngl if someone will ever see this in code they might die from cringe.

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