Migrating to React Native’s New Architecture: In-Depth Guide

Introduction 

React Native has been a favored option for developing mobile applications across platforms. Its capacity to share code between iOS and Android, along with a vast ecosystem, has turned it into a preferred choice for hire React Native developers. Nonetheless, as applications become more complex and the need for performance escalates, React Native’s previous architecture (Bridge-based) started to reveal its shortcomings. 

To address these challenges, the React Native New Architecture team is incorporating Fabric, TurboModules, and the JSI (JavaScript Interface). Transitioning to this architecture enables enhanced performance, greater compatibility with native modules, and a more contemporary basis for future expansion. 

In blog, you get a detailed guide for developers intending to transition their current React Native applications to the React Native New Architecture. 

Why Move to React Native’s New Architecture? 

Before diving into migration, it’s important to understand why this change matters. 

1. Better Performance: JSI replaces the outdated asynchronous bridge by allowing direct interaction between JavaScript and native code, greatly minimizing overhead and resulting in quicker, more responsive applications.
    
2. Fabric Renderer:  Fabric is an innovative rendering system that enhances UI uniformity while allowing for concurrent React features, offering developers a more adaptable and effective rendering workflow.
    
3. TurboModules: TurboModules introduce a new way of defining and accessing native modules, resulting in faster startup times since only the required modules are loaded.
    
4. Future-Proofing : The updated architecture aligns with React 18 capabilities such as concurrent rendering and Suspense, ensuring that applications stay maintainable, scalable, and prepared for upcoming developments. 

In summary, migrating to  React Native New Architecture keeps your app up-to-date as React Native progresses. 

Key Components of the React Native New Architecture 

1. JavaScript Interface (JSI) : JSI removes the restrictions of the previous bridge by allowing direct interactions among JavaScript, C++, and native code.
2. Fabric: a contemporary rendering engine that takes the place of the previous UI Manager, providing support for simultaneous rendering and enhancing performance.
3. TurboModules: TurboModules provide a system for lazy-loading native modules, which makes applications lighter and significantly improves startup speed.
4. Codegen: A utility that automatically creates type-safe connections between JavaScript and native code.

Migration Preparation Checklist 

Migrating isn’t simply a matter of flipping a switch. Here’s what you should do before starting: 

• Upgrade React Native: Make sure your project operates on a minimum of React Native 0.68+ (the architecture was launched in 0.68, with enhancements in subsequent versions). 

• Check Dependencies: Certain third-party libraries may still lack support for the new architecture. Check for compatibility before continuing. 

• Update Build Tools: Utilize the most recent editions of Xcode, Android Studio, and Gradle. 

• Enable Hermes: Hermes performs optimally with the new architecture, so activate it if it isn’t already enabled. 

Step-by-Step Migration Guide 

Step 1: Enable the React Native New Architecture 

For Android 

Open android/gradle.properties
 Add or enable:

newArchEnabled=true 

For iOS 

Open ios/Podfile 

Add:

use_react_native!( 

  :new_architecture_enabled => true 

) 

Run pod install inside the ios directory

Step 2: Enable Fabric 

Fabric is disabled by default. To enable: 

• Android: In MainApplication.java, ensure Fabric is enabled when new architecture is turned on

• iOS: Update AppDelegate to use Fabric renderer

Step 3: Migrate to TurboModules 

Start by recognizing the native modules in your project, and subsequently define them with the new TurboModuleSpec interface. After defining, use Codegen to automatically produce type-safe bindings that facilitate integration and minimize mistakes 

For example, create a NativeExampleSpec.js with TypeScript annotations, and Codegen will produce native bindings. 

Step 4: Test Your Application 

• Operate on both iOS and Android. 

• Pay attention to UI rendering variations, as Fabric might reveal layout problems. 

• Verify native modules to confirm they function correctly. 

Step 5: Fix Compatibility Issues 

• If some libraries do not yet support the new architecture, you may need to

• Upgrade to the most recent versions. 

• Substitute unsupported libraries with alternatives. 

• Temporarily disable the React Native new architecture implementation until the support is fully developed. 

Common Migration Challenges 

1. Library Incompatibility: Not all third-party packages currently support TurboModules or Fabric, developers may face compatibility issues. The best approach is to track progress on GitHub, use community-maintained forks, or contribute patches to help ensure smoother adoption
2. Increased Build Complexity: Enabling Codegen introduces additional steps into the build pipeline, but this complexity can be managed by automating the process with CI/CD pipelines to reduce manual effort
3. UI Bugs with Fabric:  With concurrent rendering, some UI components may behave differently than before, so it’s important to test thoroughly across devices and adjust styles or layouts wherever necessary. 

Best Practices for a Smooth Migration 

• Migrate Gradually: You can slowly embrace the new architecture by still utilizing current modules on the old system and activating new modules progressively. 

• Use Canary Builds: Test migration in a feature branch before rolling out. 

• Leverage Codegen Early: Even if your project has few native modules, using Codegen helps enforce consistency and ensures type-safe integrations throughout the app.  

• Monitor Performance: Utilize tools such as Flipper and React DevTools to assess performance before and after migration. 

The Road Ahead for React Native 

The new architecture continues to develop, but it serves as the basis for upcoming React Native features. Using Fabric, TurboModules, and JSI, developers can anticipate:  

• Better alignment with React’s core evolution. 

• Reduced overhead in bridging JS and native code. 

• More efficient memory usage and startup times. 

For developers, early adoption ensures apps remain relevant and helps avoid performance and compatibility challenges.  

Conclusion 

Migrating to React Native new architecture may appear challenging, yet it provides distinct advantages in terms of performance, scalability, and compatibility with the future of mobile development. Preparing your project, activating the new features incrementally, and thoroughly testing throughout the process can guarantee a seamless migration.  

Monitor the migration status of any third-party libraries that your app relies on. And keep in mind that migration doesn’t need to be “either/or.” You can implement Fabric, TurboModules, and Codegen gradually and in phases.  

React Native new architecture is more than a technical enhancement it represents a fundamental change that will shape the development of cross-platform applications in the future. The moment is ideal to begin organizing your migration. 

Ref link: https://www.justtechblog.com/upgrading-your-business-technology-the-benefits/