React Native + Nim

Automatic binding generation for Nim business logic in React Native apps

iOS		Android

Write your business logic in Nim, get React Native bindings automatically. Inspired by go-mobile and status-go/status-mobile.

Quick Start

Create a new project

npx create-react-native-nim my-app

Or clone and run the CLI locally:

git clone https://github.com/siddarthkay/react-native-nim.git
cd react-native-nim
node cli/bin/create-react-native-nim.js my-app

Then follow the printed steps:

cd my-app
yarn install
make build-nim        # Compile Nim + generate all bridge code
yarn ios              # or yarn android

Prerequisites

• Node.js 18+
• Nim 2.0+ (brew install nim on macOS)
• Python 3 (for binding generator)
• Xcode (iOS) / Android SDK (Android)

Or use the included Nix flake for a reproducible environment:

nix develop

Development (Demo App)

The demo app in mobile-app/ uses Makefiles for all build operations:

nix develop                        # Enter reproducible dev environment (optional)
make setup                         # Install Node dependencies
make ios                           # Build Nim backend + iOS app
make android                       # Build Nim backend + Android app
make help                          # Show all available targets

Make Targets

Target	Description
make setup	Install Node dependencies
make ios	Build Nim + iOS app (full pipeline)
make android	Build Nim + Android app (full pipeline)
make clean	Clean all build artifacts
make clean-all	Clean everything including Nim caches

Sub-project targets (run from mobile-app/):

Target	Description
make build-nim	Compile Nim + static lib + bindings + headers
make nim-compile	Compile Nim to C files only
make nim-static-lib	Compile C files into static library
make nim-bindings	Generate TypeScript/iOS/Android bridge code
make build-ios	Full iOS build pipeline
make build-android	Full Android build pipeline
make run-ios	Dev build + deploy to iOS Simulator
make run-android	Dev build + deploy to Android emulator
make clean-nim	Clean Nim build artifacts
make help	Show all targets

How It Works

Nim Source Code          Auto Generator          React Native App
(Business Logic)   -->  (Python Script)    -->  (TypeScript/UI)
   {.exportc.}          iOS + Android + TS       Type-safe calls

1. Write Nim functions

Add exported functions in nim/nimbridge.nim:

proc calculateTax*(income: cint, rate: cint): cint {.exportc.} =
  return (income * rate) div 100

proc greet*(name: cstring): cstring {.exportc.} =
  ## @allocated
  return allocCString("Hello, " & $name & "!")

2. Generate bindings

make build-nim          # from mobile-app/ or scaffolded projects

This automatically generates:

• iOS: C++ wrapper + Objective-C++ bridge + static library
• Android: JNI bridge + Kotlin TurboModule + CMake config
• TypeScript: TurboModule spec with full type safety

3. Use in React Native

import { NimCore } from './modules/nim-bridge/src/index';

const tax = NimCore.calculateTax(50000, 20);
const greeting = NimCore.greet("World");

Supported Types

Nim Type	TypeScript	Notes
cint	number	32-bit integer
int64	number	64-bit integer
cstring	string	C-compatible string
bool / cint	boolean	Use boolean_returns in config
float	number	Double precision

Project Structure

react-native-nim/
├── Makefile                 # Root orchestration (make ios, make android)
├── mobile-app/              # Demo app
│   ├── Makefile             # Build targets (build-nim, build-ios, etc.)
│   ├── nim/                 # Nim business logic
│   │   ├── nimbridge.nim    # Exported functions ({.exportc.})
│   │   └── nimbridge.nimble # Nim dependencies
│   ├── modules/nim-bridge/  # Auto-generated bridge code
│   │   ├── src/             # TypeScript TurboModule spec
│   │   ├── ios/             # Objective-C++ bridge + static lib
│   │   └── android/         # Kotlin module + JNI bridge
│   ├── src/App.tsx          # React Native app (retro terminal UI)
│   └── tools/
│       ├── generator_config.json  # Binding generator config
│       └── bindings/        # Python generator package
├── cli/                     # create-react-native-nim CLI tool
└── flake.nix                # Nix development environment

Configuration

Customize binding generation in tools/generator_config.json:

{
  "function_name_mappings": {
    "myNimFunc": "myJsName"
  },
  "boolean_returns": ["myNimFunc"],
  "type_mappings": { ... }
}

Troubleshooting

Build fails with "Symbol not found"

make clean-nim          # from mobile-app/
make build-nim
make pod-install

Metro bundler errors

yarn react-native start --reset-cache

Nim not found

nim --version  # Should be 2.0+
brew install nim  # macOS
# or use: nix develop

Architecture

• TurboModules / JSI - React Native New Architecture
• Static library (iOS) / Shared library (Android) - compiled from Nim
• Automatic code generation - no manual bridge code

License

MIT - see LICENSE.

Inspiration

• go-mobile - Go bindings for mobile
• status-mobile - Real-world Go/mobile integration
• Nim | React Native | Expo