I'm doing something Async in an iOS app. It's triggered by javascript. When it's done (somewhere separated in app), I want to let javascript know. My current solution is a native module inherited from RCTEventEmitter, which has the following method:

@interface MyEventEmitter : RCTEventEmitter
// ...
end
@implementation
- (void)giveSomethingToJS:(NSString *)something {
  [self sendEventWithName:@"SOME_NAME" body:something];
}
@end

Then, when my Async job's done, I call this method:

MyEventEmitter *emitter = [[MyEventEmitter alloc] init];
[emitter giveSomethingToJS:@{}];

And obviously, emitter.bridge is nil and the app crashed because of assert bridge != nil. So how am I supposed to get the bridge and let *emitter(the instance) know. Or how can I get the right instance with bridge initialized?

Thanks in advance!

I'm doing something Async in an iOS app. It's triggered by javascript. When it's done (somewhere separated in app), I want to let javascript know. My current solution is a native module inherited from RCTEventEmitter, which has the following method:

@interface MyEventEmitter : RCTEventEmitter
// ...
end
@implementation
- (void)giveSomethingToJS:(NSString *)something {
  [self sendEventWithName:@"SOME_NAME" body:something];
}
@end

Then, when my Async job's done, I call this method:

MyEventEmitter *emitter = [[MyEventEmitter alloc] init];
[emitter giveSomethingToJS:@{}];

And obviously, emitter.bridge is nil and the app crashed because of assert bridge != nil. So how am I supposed to get the bridge and let *emitter(the instance) know. Or how can I get the right instance with bridge initialized?

Thanks in advance!

• javascript
• ios
• objective-c
• react-native

2 Answers 2

The issue is that in the React-Native iOS SDK, RCTEventEmitter subclasses should not be initialized by you. The React-Native SDK actually handles initialization of your RCTEventEmitters.

As Arthur points out, using NSNotificationCenter to municate with your RCTEventEmitter is a good strategy. You can also create a custom singleton class and register RCTEventEmitter's with it on initialization if you need pointers to these event emitters.

I have a quick fix, not a very good idea but achieved what I want.

The problem is I can't get THE instance of MyEventEmitter, so I instead use notification center in native code to notify THE instance.

[[NSNotificationCenter defaultCenter] addObserverForName:@"NATIVE_WEIXIN_LOGIN_RESP_CODE"
                                                  object:nil
                                                  queue:nil
                                             usingBlock:^(NSNotification * _Nonnull notification) {
                                               SendAuthResp *resp = notification.object;
                                                 [self sendEventWithName:@"WEIXIN_LOGIN_RESP_CODE" body:resp.code];
                                               }];

Can you still post what the correct way in React Native to do what I want?