Scaffolding a React Native App from an Existing Next.js Frontend & REST API

Building a React Native mobile app to complement an existing Next.js web app can be accelerated by reusing code and leveraging automation tools. Instead of starting from scratch, you can generate boilerplate code from your REST APIs, share business logic between web and mobile, and use low-code platforms to scaffold your UI.

1. Leveraging API Documentation for Code Generation

If your backend provides an OpenAPI (Swagger) specification for the REST API, you can **auto-generate a typed API client** for your mobile app. Tools like Swagger Codegen or OpenAPI Generator consume the API spec and output code for calling those endpoints. This approach **eliminates a lot of boilerplate code** and ensures your client stays in sync with API changes.

Common options for codegen include:

• OpenAPI Generator CLI: Supports many languages and frameworks; for React Native you can use TypeScript generators (e.g., `typescript-fetch` or `typescript-axios`) to create a TypeScript API client.
• Swagger Codegen: Can generate client SDKs in dozens of languages. Note: Some tweaking may be needed for React Native’s environment (e.g., polyfills).
• Orval or OpenAPI Codegen for Hooks: Tools like Orval can generate React hooks tied to API endpoints (e.g., using React Query) from an OpenAPI spec.

By using these tools, much of the networking layer for your mobile app can be scaffolded. You avoid writing repetitive fetch/axios calls and focus on the UI and app logic.

2. Reusing UI/UX and Logic from the Next.js App

When moving from a Next.js web app to React Native, a key goal is to **reuse as much of the non-UI code as possible**. Web and mobile platforms have different UI requirements, but business logic can often be shared:

• Don’t Directly Reuse DOM-based UI: It's not feasible to reuse Next.js UI components. Instead, plan to rebuild the UI with React Native components, tailoring the design to mobile UX.
• Share Non-UI Code in a Monorepo: Focus on sharing **business logic, data models, and utilities** (validation schemas, API calls) in a common library. Setting up a monorepo (using Yarn workspaces or Nx) is a popular approach.
• Reuse State Management and Hooks: If your Next.js app uses state management libraries (Redux, Zustand, React Query), you can move custom hooks or store logic to the shared code (provided they don’t assume a browser DOM).
• Replicate UI/UX with Native Components: Mirror the web app’s design system (colors, spacing, typography) using a React Native component library (like React Native Paper or NativeBase) to maintain consistency.

The overall aim is to **share the core logic and avoid duplicating things like API data handling or utility functions**, but accept that you’ll implement separate UIs.

3. Implementing Authentication Flows on Mobile

Authentication in React Native will likely use the same token-based security as your web app, but tokens are handled differently on mobile:

• Secure Token Storage: **Do not store tokens in plaintext `AsyncStorage`**. Use secure storage mechanisms like **Expo SecureStore** or `react-native-keychain` (Keychain on iOS, Keystore on Android).
• Token Refresh Workflow: Implement a refresh mechanism. Use an Axios interceptor to catch 401 Unauthorized errors, automatically call the refresh token endpoint, and retry the original request. Handle logout if refresh fails.
• Auth Flow in the UI: Use React Navigation and a state/context to set up an **authentication flow** that switches between login screens (unauthenticated stack) and main app screens (authenticated stack).
• Web vs Mobile Differences: Abstract token storage behind an interface (e.g., an `AuthProvider` context) that uses platform-specific storage methods while exposing the same `getToken`, `setToken` methods to shared logic.

4. Project Structure and Maintainability

Organizing the project well is critical for long-term maintenance:

• Monorepo with Shared Code: House `apps/web` (Next.js), `apps/mobile` (React Native), and `packages/common` in one repository using Yarn Workspaces or Nx for a single source of truth.
• Modular Architecture: Structure the React Native app by feature or layer: `components`, `screens`, `services` (API clients, auth handlers), and `state` (contexts/stores).
• Consistent Typing and Interfaces: Use TypeScript and define data model types in one place, often generated from OpenAPI, ensuring consistency across both platforms.
• Maintaining the Generated Code: Script your code generation tool (e.g., "regen-api") so that client code can be refreshed easily when the backend API updates.

5. Low-Code Platforms and Additional Tools for Quick Scaffolding

Leverage low-code or visual development tools to accelerate development further:

• Draftbit: A low-code builder specifically for React Native that exports pure React Native code. You can visually create screens and integrate any REST API, then export the project to continue customizing.
• Retool Mobile: Primarily geared towards internal tools. It offers a drag-and-drop editor to assemble screens and connect them to data sources or APIs without hand-coding each component.

These platforms can rapidly produce functional UI tied into your APIs, saving you significant boilerplate UI coding.