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Talking to JSI in Swift: what changed in SDK 56

Blog post from Expo

Post Details
Company
Date Published
Author
Tomasz Sapeta
Word Count
2,611
Company Posts That Month
12
Language
English
Hacker News Points
-
Post removed?
No
Summary

Expo SDK 56 introduces significant improvements to the native module infrastructure on Apple platforms by enabling Swift to communicate directly with JSI, eliminating the need for the previous Objective-C++ intermediary layer. This change simplifies the call stack, accelerates call performance, and enhances ease of use by allowing Swift to import C++ headers directly, thus mirroring the JSI's ownership semantics with type-safe Swift APIs. The new architecture, which aligns Swift Concurrency with React Native's existing threading model, results in a substantial performance boost, particularly in asynchronous operations, making the Expo Module path faster than React Native's Turbo Modules in specific benchmarks. The update also involves prebuilt binary distribution to manage compile times and introduces the expo-modules-jsi package for iOS, tvOS, and macOS, while a separate Kotlin compiler plugin addresses Android improvements, all supported by significant contributions from AI in code coverage and testing.

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