Turbo EventEmitters

[Dunedubby]

Hi, I'm having a little trouble understanding how the new EventEmitters are working behind the scenes on iOS, and if there's a disconnect between the documentation and what actually happens. So my understanding is that every function that is created in the JSI module gets a jsi::Value __hostFunction_... function generated in the ...-generated.cpp file, as well as a virtual method declaration in the SpecJSI.h file, among other things. Should we expecting similar functions to exist for a onThingHappens JS method, after we declare a readonly onThingHappens: EventEmitter<blah>? Or is there another syntax to call these events on the JS side?

[Dunedubby]

Okay so it seems that when they get added to the separate eventEmitterMap_ object, they are then checked separately after the method checks, as shown here: https://github.com/facebook/react-native/blob/35f0e1cca2299b5816cbc1847410651eb20a3f02/packages/react-native/ReactCommon/react/nativemodule/core/ReactCommon/TurboModule.h#L143

What scenarios could cause the methodMap_ objects to be recognized as functions, but the eventEmitterMap_ objects to not?

[Dunedubby]

Actually, after investigating more, it appears that in Obj-C modules, this create() function gets overridden in https://github.com/facebook/react-native/blob/main/packages/react-native/ReactCommon/react/nativemodule/core/platform/ios/ReactCommon/RCTInteropTurboModule.mm#L249

Except this implementation doesn't even look at the eventEmitterMap_ or any reference to the event emitters at all. In other words, it seems like Obj-C Turbo modules can't access the new EventEmitter framework at all, contrary to what the docs say. @cipolleschi am I missing something?

[Dunedubby]

I was missing something: bridged/legacy-combat modules use RCTInteropTurboModule.mm, but bridgeless modules use RCTTurboModule.mm (if I understand correctly). After switching to fully bridgeless the EventEmitters seemed to connect correctly. Maybe this is worth mentioning in the docs, but at least the new EventEmitters are working with Swift, yay.