如何在 dart flutter 中返回两个字符串值

Question

我正在处理我想使用共享首选项的 flutter 项目。看下面的代码：

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

这是我的 getCredentials 函数 我希望此函数将电子邮件和密码作为不同的参数返回，但 dart 不允许我可以请你帮助我我该怎么做？

整个 SharedPreference 代码：

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;
  }
}

Answer 1

只需创建类。您甚至可以稍后将方法添加到 Credentials。就像安全比较一样，将 passwordHash 与常数时间进行比较。

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));
}

编辑使用 crypto 获取密码的哈希值：

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

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

Answer 2

将返回类型 String 更改为 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

};
}