FRP at Kickstarter and Kotlin

Summary

Kickstarter’s open-source iOS and Android apps use Functional Reactive Programming (FRP) patterns to keep views simple and move mutation and complex logic into thoroughly tested ViewModels. The post describes how this discipline helped a developer ramp up quickly on the Android codebase after working on Kickstarter’s backend and payments teams. It also introduces the Android team’s interest in Kotlin, a JetBrains language that runs on the JVM, while noting that dependency concerns had prevented conversion of core functionality. For a 2017 Functional Swift Conference talk in Berlin, the author used Kotlin to add a simple Android screen following the team’s established FRP patterns, presenting the implementation as live coding and an introduction to FRP and Kotlin.

Takeaways

1. 1

   FRP places mutation and complex logic in ViewModels, which Kickstarter thoroughly tests while keeping views simple.

2. 2

   Following FRP patterns across the mobile codebase helped the author ramp up quickly on Kickstarter’s Android team.

3. 3

   Kickstarter had added some Kotlin classes to its Android app, but dependency concerns had blocked conversion of core functionality.