native-module-helper

# Native Module Helper

Build custom native modules to bridge JavaScript and native code in React Native.

## Quick Start

Native modules expose native functionality to JavaScript. Choose based on React Native version:
- **Legacy Bridge**: RN < 0.68 (stable, widely supported)
- **Turbo Modules**: RN >= 0.68 (better performance, type-safe)

## Instructions

### Step 1: Plan Module Interface

**Design JavaScript API:**
```javascript
// What you want to call from JS
import { NativeModules } from 'react-native';
const { MyModule } = NativeModules;

// Synchronous
const result = MyModule.getValue();

// Asynchronous (Promise)
const data = await MyModule.fetchData();

// With callback
MyModule.processData(input, (error, result) => {
  if (error) console.error(error);
  else console.log(result);
});

// Event emitter
MyModule.addListener('onUpdate', (event) => {
  console.log(event);
});
```

**Keep bridge calls minimal:**
- Batch operations when possible
- Avoid frequent small calls
- Use events for continuous updates

### Step 2: Create Module Structure

**File structure:**
```
MyModule/
├── ios/
│   ├── MyModule.h
│   ├── MyModule.m (or .swift)
│   └── MyModule-Bridging-Header.h (if Swift)
├── android/
│   └── src/main/java/com/mymodule/
│       ├── MyModulePackage.java
│       └── MyModule.java (or .kt)
├── js/
│   └── NativeMyModule.ts
└── package.json
```

### Step 3: Implement iOS Module

**Objective-C (.h file):**
```objc
#import <React/RCTBridgeModule.h>
#import <React/RCTEventEmitter.h>

@interface MyModule : RCTEventEmitter <RCTBridgeModule>
@end
```

**Objective-C (.m file):**
```objc
#import "MyModule.h"

@implementation MyModule

RCT_EXPORT_MODULE();

// Synchronous method
RCT_EXPORT_BLOCKING_SYNCHRONOUS_METHOD(getValue)
{
  return @"value";
}

// Async with Promise
RCT_EXPORT_METHOD(fetchData:(RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject)
{
  // Perform operation
  if (success) {
    resolve(@{@"data": result});
  }