Example using GSEventEmitter

GSBeaconManager.h

#import <Foundation/Foundation.h>
#import "RCTBridge.h"

@interface GSBeaconManager : NSObject <RCTBridgeModule>

@end

GSBeaconManager.m

#import "GSBeaconManager.h"
#import "GSEventEmitter.h"
#import <Gimbal/Gimbal.h>

@interface GSBeaconManager () <GMBLBeaconManagerDelegate>

@property (nonatomic, strong) GMBLBeaconManager *beaconManager;

@end

@implementation GSBeaconManager

RCT_EXPORT_MODULE();

RCT_EXPORT_METHOD(startListening){
  [[self beaconManager] startListening];
}

- (instancetype)init {
  self = [super init];
  if (self) {
    [Gimbal setAPIKey:kGMBLKey options:nil];
    _beaconManager = [GMBLBeaconManager new];
    _beaconManager.delegate = self;
  }
  return self;
}

- (void)beaconManager:(GMBLBeaconManager *)manager didReceiveBeaconSighting:(GMBLBeaconSighting *)sighting {
  NSString *beaconID = sighting.beacon.identifier;
  [GSEventEmitter application:[UIApplication sharedApplication] beaconSighted:beaconID];
}

@end

Welcome.js

import React, { Component, PropTypes } from 'react';
import { NativeModules, NativeEventEmitter } from 'react-native';
  
class Welcome extends Component {
  constructor(props) {
    super(props);
    this.eventEmitter;
  }
  
  componentWillMount() {
    const { GSBeaconManager, GSEventEmitter } = NativeModules;
    const { addBeacon } = this.props.actions;

    this.eventEmitter = new NativeEventEmitter(GSEventEmitter);
    this.eventEmitter.addListener(GSEventEmitter.SIGHTED_BEACON, (data) => addBeacon(data.payload));

    GSBeaconManager.startListening();
  }
  
  componentWillUnmount() {
    this.eventEmitter.remove();
  }
  
  ...
}

Thanks! This was really helpful for me 🥇