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Ramanpreet Nara
ef512194a6
Summary: Before invoking TurboModule ObjC methods, we loop through all the arguments and transform them from `jsi::Value` to ObjC data structures. `jsi::Value`s that represent JS Objects get converted to `NSDictionary`s in ObjC. This isn't good enough because `NSDictionary` isn't typed. What we really need is a C/C++ struct that represents the type of the JS Object. Therefore, for every argument of a TurboModule method that is a JS Object, this diff allows you to specify a method on `RCTCxxConvert` (which you have to declare and implement) that transforms that type of JS Object into something else. Basically, with the changes in this diff, we'll be able to transform JS Objects into C++ struct instances, which gives us type safety for JS Object method argumetns to TurboModule functions. I modified the codegen to also create a mapping from NativeModule method name => argument num => `RCTCxxModule` conversion selector. This way, the FB codegen that generates the `RCTCxxConversion` function also informs our TurboModule system which conversion function to use before we call the method requiring complex argument. I just had to extend the `ObjCTurboModule` class to accomplish this. The old system relies on the additional method generated by `RCT_EXPORT_METHOD` macro. It takes the written code, does string processing on it to parse the type of the struct arguments, and then replaces all instances of `::` with `_`. Super hacky. I didn't take this approach because it seemed unnecessarily hacky brittle. The other approach I considered was to try to use reflection to infer the type of the struct at runtime. We'd have to do a bit of string processing and concat the TurboModule class name with the struct type. The solution would be simpler because it'd only modify the objective C and it wouldn't touch the Codegen system. **Edit:** I implemented it here: D14513078. The one downside of this design is that the name of the conversion function is individually constructed in two different locations in the code (i.e: no source of truth for this name). The other downside is that we have to rely on `RCTBridgeModuleNameForClass`, which we want to eliminate. This also computationally more expensive since it requires string processing/regex parsing and additional reflection. Therefore, we decided to move on with the current solution. Reviewed By: fkgozali Differential Revision: D14513429 fbshipit-source-id: 3d1b87e02ee908a19305686ff82b2ed624d8ac67