This differential implements CommServicesAuthMetadataEmitter for iOS in such a way that it is callable from C++.
Details
Details
- Apply this patch: https://gist.github.com/marcinwasowicz/7f04bd592dd4a800adbc96b720e200b7. It creates js code to subscribe for auth metadata events and sends this event from C++ upon each draft update (contents of the event are just dummy strings).
- Build iOS app.
- Ensure that each time you write one letter you can see console.log with dummy auth metadata in native yarn dev terminal.
Diff Detail
Diff Detail
- Repository
- rCOMM Comm
- Lint
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React native requires that event emitter is an instance of a class. On the other hand in order to smoothly call this object from Rust we need static method. Therefore I decided to use Singleton pattern for Rust <-> C++ interop. Object that is available to for C++ and Rust is set when the first JS listener subscribes and is removed when the last listener unsubscribes. This way we ensure that Rust/C++ won't try to send event if value under sharedInstance might be invalid. All calls that access or mutate sharedInstance are synchronized on class level.
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Reviewers can quickly and easily familiarise themselves with event emitter implementation on iOS by reading the doc: https://reactnative.dev/docs/native-modules-ios#sending-events-to-javascript.
| native/ios/Comm/CommServicesAuthMetadataEmitter.mm | ||
|---|---|---|
| 9 ↗ | (On Diff #34633) | It might look uncommon to have interface declaration and implementation next to each other in a single file but in fact we don't need to expose CommServicesAuthMetadataIOSWrapper. If we want to call sendAuthMetadataToJS from Objective - C we can use the common C++ API so let's avoid creating unnecessary files and duplication the same API. |
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Have you tested sending events (calling sendAuthMetadataToJS) when there are no listeners? Looking at the code, it should work but I want to make sure it doesn't crash the app
That makes sense
| native/ios/Comm/CommServicesAuthMetadataEmitter.mm | ||
|---|---|---|
| 9 ↗ | (On Diff #34633) | It's not that uncommon 😉 I've seen this pattern already in some RN-related code and it makes sense here |
| 13–15 ↗ | (On Diff #34633) | What about sendAccessTokenToJS: ... withUserID: ... withDeviceID? Initially, I got confused because I understood sendToJSAccessToken as "send something to JS-based access token" 😅 |
| native/ios/Comm/CommServicesAuthMetadataEmitter.mm | ||
|---|---|---|
| 13–15 ↗ | (On Diff #34633) | +1 |
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- Rename Obj-C method.
- Use commServicesAccessToken instead of accessToken to match JS-types.
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I am really sorry for omitting this comment - it wasn't intentional.
I executed test where C++ code kept sending events on each character typed but there were no JS-listeners. Nothing happened.