Скачать или смотреть Solving NSInvalidArgumentException: How to Fix the Flutter and Firebase Crash on iOS

In this guide, we tackle the frustrating `NSInvalidArgumentException` error in your Flutter app caused by Firebase integration. Discover the root cause, effective solutions, and helpful tips to get your app running smoothly on iOS devices.
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Introduction

Are you facing the distressing NSInvalidArgumentException crash in your Flutter app when running it on an actual iOS device? If your application works seamlessly on an emulator but experiences a fatal error with the message -[NSNull length]: unrecognized selector sent to instance, you're not alone. Many developers have run into similar issues, especially after integrating Firebase services.

In this guide, we'll dive deep into this error message, analyze its cause, and walk you through the solution step-by-step.

Understanding the Error Message

When you see the error message like:

[[See Video to Reveal this Text or Code Snippet]]

It indicates that the app is attempting to call the length method on an instance of NSNull, which is not valid. This suggests that somewhere in your Flutter code, a null value is being pushed where a string (that includes a length method) is expected.

Problem Overview

Background

After updating your Flutter application and adding the firebase_messaging package, it seems everything works well in an emulator, but crashes when deployed on an actual device. You've already enabled essential settings such as "Push Notifications" and "Background Fetch" in Xcode, and you’ve even removed Firebase messaging without success.

Root Cause

The critical issue arises due to null safety changes in Flutter. Attempting to pass a null value to the native Firebase SDK will result in a crash rather than a simple error notification. This means that if you're not checking for null values correctly in your shared preferences or similar data sources, it can lead to the violent crash you're experiencing.

Finding a Solution

The following steps outline how to resolve this issue:

1. Identify Where Null Values Are Passed

Start by thoroughly inspecting your Flutter code, especially where you are calling Firebase methods. Pay special attention to:

Functions related to authentication (e.g., sign-in functions).

Shared preference data retrievals.

2. Implement Null Checks

Wherever you are dealing with user input or data fetching, ensure that you are implementing null checks. For example:

[[See Video to Reveal this Text or Code Snippet]]

3. Test Your Changes

Once you've identified possible sources of null values and made necessary changes:

Rebuild your application.

Test it on a real iOS device to ensure the crash no longer occurs.

4. Further Debugging

If the problem persists, increase your debugging efforts. You can use tools like print statements or logging packages to trace the application's flow and see where the null values might be arising.

5. Reach Out to the Community

If after following these steps you're still encountering issues, don't hesitate to reach out to developer forums, GitHub issues, or community groups. They can provide insights or solutions based on their experiences.

Conclusion

Dealing with null safety in Flutter, especially in conjunction with Firebase services, can be challenging. By understanding the NSInvalidArgumentException error and following a systematic approach to identify and handle null values, you can effectively solve this problem and ensure your app runs smoothly on any device.

If you've faced a similar issue or have tips to share, feel free to leave a comment below. Together, we can help each other overcome these hurdles in app development!