Recommended APIs for events in Turbo Modules

[joemun]

👋 I'm having trouble finding official guidance/examples on the migration path for event emitters from Native Modules to Turbo Modules. Per https://reactnative.dev/docs/native-modules-android#sending-events-to-javascript, do Turbo Modules still support adding JS event listeners using NativeEventEmitter?

Is it possible to define listeners in the JS spec? And for Android, what should the implementation look like? (ie. still create functions for @ReactMethod addListener and @ReactMethod removeListeners?)

Thanks!

[flokol120]

@joemun Maybe take a look here: https://github.com/react-native-community/RNNewArchitectureLibraries/tree/feat/swift-event-emitter (If you did not know it existed :) )

It's for iOS only unfortunately, but it states:

Note: The addListener and removeListeners implementations will be provided by React Native.

But I've already noticed, that the Android Spec Interface forces you to implement addListener as well as removeListeners . However you can just leave the implementations empty. At least it worked in my use case. But I'd also like to know if this is intentional :D.

[joemun]

Thanks for responding. Yes, I'm primarily interested in the Android side.

Looks like event emitting still works when passing a turbo module into a NativeEventEmitter, and using its addListener API. But I'm curious about whether this is the long-term API that uses the new JSI when New Arch is enabled, or is this only working because the legacy bridge is still in place.

[cortinico]

The recommended API to dispatch events in the New Architecture (and also in the old one) on Android is the Event Dispatcher. You can find an example of its usage here: #137 (comment)

[DanielFrTB]

@cortinico Is there any example for using events on iOS using TurboModules ?

[cipolleschi]

@DanielFrTB have a look at this doc: https://github.com/reactwg/react-native-new-architecture/blob/main/docs/turbo-modules.md#add-event-emitting-capabilities

This is for 0.76 and typed EventEmitters. Untyped event emitters should also be available on previous versions on React Native (<0.76) but we forgot to expose the TS type for the EventEmitter, so you'll probably see a type not found error, but it should actually work.

[DanielFrTB]

Thanks @cipolleschi

[abumubaarak]

@cipolleschi can you perhaps give an example for (<0.76)?

Thanks

[abumubaarak]

@cipolleschi Following the example at test_fixtures for NATIVE_MODULE_WITH_EVENT_EMITTERS does not generate anything.