Скачать или смотреть Resolve the 'Native module cannot be null' Error in React Native by Switching to Bare Workflow

Learn how to fix the '`Native module cannot be null`' error in your React Native project by understanding the requirements for using `react-native-fs` and switching to the Bare workflow.
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Understanding the Native module cannot be null Error in React Native

If you're developing a mobile application using React Native, you might encounter various errors during your coding journey. One such common issue is the error message stating Invariant Violation: Native module cannot be null. This error often surfaces when working with native modules, and it can come across as a roadblock, especially for developers who are using the Expo framework.

In this post, we will delve into this error, understand what causes it, and share a structured solution for overcoming it, particularly when working with the react-native-fs library.

The Root of the Problem

You may receive the Native module cannot be null error when trying to use a native module that requires linking or native capabilities that aren't available in Expo's managed workflow. For example, you may try to utilize the react-native-fs module to manage file systems in React Native, and receive this error resulting from the following code:

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Why the Error is Occurring

Expo Managed Workflow: The code utilizes the react-native-fs library, which is a native module and requires native code linking. Unfortunately, when using Expo's managed workflow, you do not have direct access to native code linking required by certain libraries like react-native-fs.

Native Dependencies: If a module relies on such native capabilities but your project is set up in a managed environment, you won't be able to successfully use that module, leading to the error.

Solution: Transitioning to Bare Workflow

To resolve the issue and effectively use react-native-fs, you will need to transition your Expo project from a managed workflow to the Bare workflow. Below are the steps to achieve that:

Step 1: Eject from the Managed Workflow

Open Your Terminal: Navigate to your Expo project directory.

Run the Command: Execute expo eject. This command will generate the necessary Android and iOS folders to enable you to work with native code.

Step 2: Install react-native-fs

Once you've ejected, you can install the react-native-fs module without issues by running:

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or

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Step 3: Linking the Module

After installing, ensure that the module is correctly linked:

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Step 4: Adding Configuration (if necessary)

In some cases, additional setup may be required in the android and ios folders. Make sure to check the official documentation of react-native-fs for any platform-specific configurations.

Step 5: Rebuild the Project

Lastly, from your terminal navigate to the root of your project and run:

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

or

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

Conclusion

Switching from Expo's managed workflow to the Bare workflow can seem daunting at first, but it’s a necessary step when relying on certain native modules like react-native-fs. By following the outlined steps, you can resolve the Native module cannot be null error and successfully implement file system operations in your React Native application.

Feel free to reach out in the comments if you encounter any issues or have questions regarding the process. Happy coding!