Instagram's Instant Feedback in iOS Engineering Workflows
Original post Instant Feedback in iOS Engineering Workflows
Article Summary
Instagram engineers were losing hours every day waiting for code to compile. So they brought React Native's ⌘R instant refresh experience to native iOS.
Instagram's iOS team built a custom hot-reloading system that lets engineers see native Objective-C code changes in seconds instead of minutes. The tool uses dynamic library loading and Objective-C runtime APIs to swap method implementations while the app runs.
Key Takeaways
- Engineers see changes up to 20x faster than full app restarts
- Dynamic libraries load new code into running iOS simulator apps
- Objective-C runtime APIs swap method implementations without restarting
- ComponentKit views update instantly while preserving all app state
- Only modified files compile and link, making iteration nearly instant
Instagram's native code reloading tool delivers sub-second feedback loops for iOS engineers, eliminating the compile-link-install-launch cycle that previously consumed significant development time.
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What This Article Covers
Instagram engineers working on native Objective-C code had to recompile, link, install, and relaunch the app after every change. This created constant context-switching and hurt productivity as the codebase grew.
Instagram Engineering built a native code reloading system that compiles only the files you changed into dynamic libraries. It then uses the Objective-C runtime to swap out method implementations in the running iOS simulator without needing a restart.
Engineers using ComponentKit can now see changes to UI layout code in seconds. Larger apps see up to twenty times faster feedback compared to doing a full restart cycle.
This page summarizes “Instant Feedback in iOS Engineering Workflows” by Instagram, published Jun 6, 2023. All credit for the original work goes to the authors.
