IOS: You must override the `supportedEvents` method Error thrown when `supportedEvents` is implemented in super class

[saumitrabhave]

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Environment

Environment:
OS: macOS High Sierra 10.13.2
Node: 9.11.1
Yarn: Not Found
npm: 5.6.0
Watchman: 4.9.0
Xcode: Xcode 9.2 Build version 9C40b
Android Studio: 3.0 AI-171.4443003

Packages: (wanted => installed)
react: 16.3.1 => 16.3.1
react-native: 0.55.2 => 0.55.2

Description

RCTEventEmitter has a check implemented in class initializer to check that the Implementation being created implements 'supportedEvents' method. this is achieved here

But the RCTClassOverridesInstanceMethod method defined here uses class_copyMethodList obj-C Runtime method to get instance methods and iterate over them to see if required method is implemented.

as per Apple Docs class_copyMethodList does NOT return instance methods implemented by super classes.

This causes the app to crash in Dev mode (because of RCTAssert?) if the app has its own hierarchy of RCTEventEmitters, in which case the supportedEvents is implemented by an intermediate superclass between the current class and RCTEventEmitter.

IMO, the implementation should walk the inheritance hierarchy till RCTEventEmitter to make the correct assertion.

Reproducible Demo

Create a Native Module with One BaseEmitter which extends from RCTEventEmitter implement all the required functionalities also the supportedEvents method. Now create another class MainEmitter which extends from BaseEmitter, do not implement the supportedEvents method in MyEmitter to re-use implementation from BaseEmitter

App will crash on first use of MainEmitter

[react-native-bot]

Can you reproduce the issue on the latest release, v0.56?

[saumitrabhave]

@react-native-bot Yes I can reproduce this issue in latest version as well.

[hramos]

Can you update your original issue accordingly?

[react-native-bot]

I am closing this issue because it does not appear to have been verified on the latest release, and there has been no followup in a while.

If you found this thread after encountering the same issue in the latest release, please feel free to create a new issue with up-to-date information by clicking here.