Improving Animations on iOS with Stagehand

Cash App just open-sourced Stagehand, their solution to a problem that's plagued iOS developers since 2008: building animations shouldn't feel like archaeology.

Nick Entin from Cash App traces the messy evolution of iOS animation APIs (from CoreAnimation's stringly-typed key paths to UIKit blocks) and introduces their modern Swift framework that finally brings compile-time safety and composability to animation development.

Key Takeaways

• Stagehand uses Swift key paths for compile-time safe animations, no more type-erased values
• Composable structure lets you build complex multi-part animations from reusable components
• Construction separates from execution: define animations before creating the views to animate
• Visual snapshot testing for animations catches regressions with GIF comparisons
• Works with custom types via protocol conformance, not just views and layers

The demo app shows how Cash App uses this internally for screen transitions, and the testing approach could change how teams prevent animation regressions.