You shouldn't init RCTCameraEvent yourself. It will be initialized by react native. You must try to communicate with that instance in some way. For example your AppDelegate may send a notification which RCTCameraEvent subscribes to on init. You may then forward that information to js using the [self sendEventWithName:@"CustomEvent" body:@{@"name": @"111"}];

I agree this is a bit tricky and some help from the framework and documentation would be nice

This is also a very nice way. https://gist.github.com/brennanMKE/1ebba84a0fd7c2e8b481e4f8a5349b99 I think this is exactly what you are looking for?

Finally, I got the solution.

#import "RNNotification.h"
@implementation RNNotification

RCT_EXPORT_MODULE();

+ (id)allocWithZone:(NSZone *)zone {
    static RNNotification *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [super allocWithZone:zone];
    });
    return sharedInstance;
}

- (NSArray<NSString *> *)supportedEvents
{
    return @[@"EventReminder"];
}

- (void)sendNotificationToReactNative
{
    [self sendEventWithName:@"EventReminder" body:@{@"name": @"name"}];
}

When you use it!

RNNotification *notification = [RNNotification allocWithZone: nil];
[notification sendNotificationToReactNative]

Yep, singleton pattern is one option.

you save my day @Liqiankun
thank you!

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@Liqiankun I did the same thing as you, still getting a damn error in my AppDelegate No visible @interface for 'RTNEventManager' declares the selector 'socketOpenConnection:userNumber:'

These are my files:

RTNEventManager.h

#import <React/RCTBridgeModule.h>
#import <React/RCTEventEmitter.h>

@interface RTNEventManager : RCTEventEmitter <RCTBridgeModule>

@end

RTNEventManager.m

#import "RTNEventManager.h"

@implementation RTNEventManager

RCT_EXPORT_MODULE();

+ (id)allocWithZone:(NSZone *)zone {
    static RTNEventManager *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [super allocWithZone:zone];
    });
    return sharedInstance;
}

- (NSArray<NSString *> *)supportedEvents
{
  return @[@"onOpened"];
}

- (void)socketOpenConnection
{
  [self sendEventWithName:@"onOpened" body:@{@"callername": @"205-966-1916", @"username": @"9542493959"}];
}

@end

and then inside my AppDelegate.m I do this

#import "RTNEventManager.h"
...
RTNEventManager *manager = [RTNEventManager allocWithZone: nil];
[manager socketOpenConnection];

And when building it pops up the same error again and again.

expose an interface like this

'- (void) socketOpenConnection'

in your ".h" file