2026-07-105 min read
By Lester Romero Bernardo · Reviewed technical guidance
How to identify performance issues in a SwiftUI app
1. Understanding the SwiftUI Render Cycle
SwiftUI is declarative: views are a function of their state. When state changes, SwiftUI re-evaluates the view's body. If body evaluation is heavy or triggered too often, the UI stutters and battery consumption spikes.
2. Profiling with Xcode Instruments
Don't guess where bottlenecks are. Use Time Profiler and the SwiftUI Views Instrument to track:
- Slow Frames: Screen updates exceeding the 8.3ms frame budget (for 120Hz/ProMotion screens).
- Redundant Body Computations: Views whose body property is evaluated even when visible data remains unchanged.
- Main Thread Hangs: Heavy CPU work (like JSON parsing or local database querying) running directly on the main thread.
3. Data Model Optimisation
To prevent redundant renders, keep views focused and pass only required data. Instead of passing a large observable object down the entire hierarchy, slice your models or use value types for child components.