Functional Reactive Programming On Mobile: A Rosetta Stone

Nick Tinsley from Squarespace shows how the same reactive programming patterns work across iOS, Android, and React Native. Think Excel formulas, but for your entire mobile app.

Squarespace's mobile team breaks down Functional Reactive Programming (FRP) by building the same app three times: once with ReactiveCocoa for iOS, once with RxJava for Android, and once with MobX for React Native. The article serves as a practical Rosetta Stone for understanding how Observables, Signals, and Streams work across platforms.

Key Takeaways

• FRP treats data like Excel: change one cell, all dependent cells update automatically
• ReactiveCocoa and RxJava share nearly identical patterns for filter, map, and subscribe operations
• MobX takes a different approach, focusing on observable state rather than event streams
• Multiple subscriptions let you update UI and send server requests from the same data stream

The article includes a clever example involving rapper RiFF RAFF's unique capitalization style that demonstrates how to chain transformations in reactive streams.