Are you tired of encountering the dreaded “Type LegacyJavaScriptObject is not a subtype of FutureOr<CryptoKey>” error when using Flutter Secure Storage for web? You’re not alone! In this comprehensive guide, we’ll delve into the world of secure storage, explore the causes of this error, and provide step-by-step solutions to get you back on track.
- What is Flutter Secure Storage?
- The Error: Type LegacyJavaScriptObject is not a Subtype of FutureOr<CryptoKey>
- Solution 1: Use the `flutter_secure_storage_web` Package
- Solution 2: Use the `js` Library to Convert the `LegacyJavaScriptObject`
- Solution 3: Downgrade to an Earlier Version of the Plugin
- Conclusion
- FAQs
What is Flutter Secure Storage?
Flutter Secure Storage is a popular plugin that allows developers to store sensitive data, such as API keys, tokens, and encryption keys, securely on various platforms, including mobile and web. It utilizes the platform’s native security features, like Keychain on iOS and SharedPreferences on Android, to protect your app’s sensitive information.
The Error: Type LegacyJavaScriptObject is not a Subtype of FutureOr<CryptoKey>
The error “Type LegacyJavaScriptObject is not a subtype of FutureOr<CryptoKey>” typically occurs when you’re trying to use the Flutter Secure Storage plugin on the web platform. This error is caused by a mismatch between the return type of the `getCryptoKey` function and the expected type.
Why does this error occur?
The error occurs because the `getCryptoKey` function returns a `LegacyJavaScriptObject`, whereas the expecting type is `FutureOr
Solution 1: Use the `flutter_secure_storage_web` Package
One solution is to use the `flutter_secure_storage_web` package, which is specifically designed for web platforms. This package provides a compatible implementation of the `flutter_secure_storage` plugin for the web.
Here’s how to use it:
dependencies:
flutter_secure_storage_web: ^2.0.2
Import the package in your Dart file:
import 'package:flutter_secure_storage_web/flutter_secure_storage_web.dart';
Create an instance of the `FlutterSecureStorageWeb` class:
final storage = FlutterSecureStorageWeb();
Now, you can use the `storage` object to store and retrieve sensitive data securely.
Solution 2: Use the `js` Library to Convert the `LegacyJavaScriptObject`
If you’re using the `flutter_secure_storage` plugin directly, you can use the `js` library to convert the `LegacyJavaScriptObject` to a `CryptoKey`.
First, add the `js` library to your `pubspec.yaml` file:
dependencies:
js: ^0.6.3
Import the `js` library in your Dart file:
import 'package:js/js.dart';
Create a function to convert the `LegacyJavaScriptObject` to a `CryptoKey`:
@JS('CryptoKey')
class CryptoKey {}
FutureOr convertLegacyObjectToCryptoKey(LegacyJavaScriptObject obj) {
return CryptoKey.from(obj);
}
Now, you can use this function to convert the `LegacyJavaScriptObject` returned by the `getCryptoKey` function:
final cryptoKey = await convertLegacyObjectToCryptoKey(await storage.getCryptoKey());
This will convert the `LegacyJavaScriptObject` to a `CryptoKey`, which can be used to store and retrieve sensitive data securely.
Solution 3: Downgrade to an Earlier Version of the Plugin
If you’re not comfortable with the above solutions, you can try downgrading to an earlier version of the `flutter_secure_storage` plugin.
dependencies:
flutter_secure_storage: ^5.0.2
This version of the plugin does not return a `LegacyJavaScriptObject`, so you won’t encounter the error. However, keep in mind that this might not be the most secure or up-to-date solution.
Conclusion
In this article, we’ve explored the causes of the “Type LegacyJavaScriptObject is not a subtype of FutureOr<CryptoKey>” error when using Flutter Secure Storage for web. We’ve provided three solutions to overcome this error: using the `flutter_secure_storage_web` package, converting the `LegacyJavaScriptObject` using the `js` library, and downgrading to an earlier version of the plugin.
By following these solutions, you should be able to use Flutter Secure Storage to store sensitive data securely on the web platform. Remember to always prioritize security and use the most up-to-date and secure solutions available.
FAQs
Q: What is the most secure solution for storing sensitive data on the web?
A: Using the `flutter_secure_storage_web` package, which is specifically designed for web platforms, is the most secure solution.
Q: Can I use the `js` library to convert the `LegacyJavaScriptObject` on mobile platforms?
A: No, the `js` library is specifically designed for web platforms, and you should not use it on mobile platforms.
Q: What if I’m already using the `flutter_secure_storage` plugin on mobile platforms?
A: You can continue using the `flutter_secure_storage` plugin on mobile platforms, and use the `flutter_secure_storage_web` package or the `js` library solution on the web platform.
Frequently Asked Question
If you’re struggling with the “type LegacyJavaScriptObject is not a subtype of FutureOr<CryptoKey>” error when using flutter_secure_storage for web, don’t worry, we’ve got you covered! Here are some frequently asked questions to help you troubleshoot the issue.
What is the main reason behind the “type LegacyJavaScriptObject is not a subtype of FutureOr<CryptoKey>” error?
The error occurs because the `flutter_secure_storage` package uses JavaScriptObjects, which are not compatible with the `CryptoKey` type expected by the `get()` method. This mismatch in data types causes the error.
How can I fix the error when using `flutter_secure_storage` for web?
To fix the error, you need to cast the result of the `get()` method to a `CryptoKey` type. You can do this by using the `as` keyword, like this: `final key = storage.read(‘key’) as CryptoKey;`.
Is there a way to avoid this error in the first place?
Yes, you can avoid this error by using a different storage solution that is compatible with the `CryptoKey` type. For example, you can use the `dart:crypto` library to generate and store cryptographic keys.
What is the impact of this error on my application’s security?
The error itself does not compromise your application’s security. However, if you’re not handling cryptographic keys correctly, it can lead to security vulnerabilities. Make sure to follow best practices for key management and storage to ensure the security of your application.
Where can I find more resources to learn about secure storage in Flutter?
You can find more resources on secure storage in Flutter by checking out the official Flutter documentation, as well as online tutorials and forums. Additionally, you can explore other secure storage solutions, such as the `flutter_secure_storage` package, to find the one that best fits your needs.
