Modernizing Legacy React Native App for App Store Compliance

A comprehensive guide to upgrading a legacy React Native application to meet current App Store standards, detailing challenges, solutions, and best practices.

Introduction

In the rapidly evolving landscape of mobile app development, maintaining legacy applications can present significant challenges. This article details my recent experience upgrading a legacy React Native application to meet current App Store requirements, offering insights and strategies for developers facing similar tasks.

The Challenge

In April 2020, Apple implemented new guidelines requiring all app submissions to be built with Xcode 11, which itself necessitated macOS Mojave 10.14.3 or later. This update posed a particular challenge for one of our clients, whose application was built using React Native version 0.47.1 – a version significantly outdated by current standards.

Our objective was clear: upgrade the application from React Native 0.47.1 to 0.63.2 to ensure compatibility with Xcode 11 and, by extension, compliance with the new App Store requirements.

Approach and Methodology

To tackle this complex upgrade process, we developed a structured approach:

1. Effective Version Control: Created a separate branch for the upgrade process, allowing us to work independently of the main production code. Established a clear branching strategy, enabling us to isolate and manage changes effectively. Implemented comprehensive tagging for each stable point in the upgrade process, providing clear rollback points if needed.
2. Incremental Upgrades: Rather than attempting a direct jump from 0.47.1 to 0.63.2, we planned a series of incremental updates. This approach allowed us to address issues at each stage, making the process more manageable and reducing the risk of introducing complex, hard-to-diagnose problems.
3. Dependency Management: With each incremental update, we conducted a thorough review of all dependencies. This process involved updating compatible libraries, finding alternatives for deprecated ones, and in some cases, refactoring code to remove unnecessary dependencies.
4. Rigorous Testing Protocol: We implemented a comprehensive testing strategy that included:
   • Automated testing to catch breaking changes quickly
   • Extensive manual testing to identify subtle UI/UX issues
   • Performance testing to ensure the app maintained or improved its efficiency
5. Detailed Documentation: Throughout the upgrade process, we maintained comprehensive documentation of each step, including challenges encountered and their respective solutions. This documentation serves as a valuable resource for future upgrades and for onboarding new team members.

Key Challenges and Solutions

1. API Changes and Deprecations

Challenge: Significant changes in React Native's API between versions 0.47.1 and 0.63.2.

Solution: We created a comprehensive list of API changes and methodically updated our codebase. This often involved refactoring large portions of the code to align with new best practices.

2. Third-Party Library Compatibility

Challenge: Many third-party libraries used in the original application were no longer compatible with newer React Native versions.

Solution: We adopted a three-pronged approach:

• Updating libraries where newer, compatible versions were available
• Finding and integrating alternative libraries where updates weren't available
• In some cases, internalizing the functionality of deprecated libraries

3. Build Process Updates

Challenge: The build process required significant updates to work with the new React Native version and Xcode 11.

Solution: We rewrote substantial portions of the build scripts, updated the Podfile for iOS, and modified the Gradle configuration for Android to ensure smooth building and deployment processes.

Lessons Learned and Best Practices

1. Proactive Maintenance: Regular, incremental updates can prevent the accumulation of technical debt and make future upgrades less daunting.
2. Comprehensive Documentation: Thorough documentation of the codebase and upgrade process is invaluable, especially in long-term projects where team composition may change.
3. Community Engagement: The React Native community proved to be an invaluable resource. Engaging with the community through forums, GitHub issues, and official documentation significantly eased the upgrade process.
4. Balanced Testing Approach: While automated tests are crucial, the importance of thorough manual testing cannot be overstated, especially for catching subtle UI/UX issues.
5. Flexibility in Problem-Solving: Maintaining flexibility in our approach allowed us to pivot when faced with unexpected challenges, ultimately leading to more effective solutions.

Conclusion

Upgrading legacy React Native applications to meet current standards is a complex but necessary process. It requires a structured approach, in-depth knowledge of both the old and new systems, and a willingness to engage in creative problem-solving.

By following the methodology outlined in this article and remaining adaptable throughout the process, developers can successfully modernize legacy applications, ensuring they remain compliant with current requirements and ready for future enhancements.

As the mobile development landscape continues to evolve, the ability to effectively manage and upgrade legacy code will remain a crucial skill for developers and a key consideration for businesses looking to maintain their mobile presence.