app startup time optimisations

To optimize app startup time, Apple provides several tools and techniques discussed in various WWDC sessions. Here are some key points:

1. Xcode Recommendations: In the session "What’s new in Xcode," it was mentioned that Xcode provides metric recommendations for app launch time. For example, if your app's launch time is measured at 564 milliseconds, Xcode might recommend aiming for 425 milliseconds. This gives developers a clear target to optimize towards. Xcode's build system improvements, such as enabling explicitly built modules for Swift code, can also help optimize the build pipeline, potentially reducing launch times. What’s new in Xcode (27:33)

2. SwiftUI Performance: In the session "Optimize SwiftUI performance with Instruments," it was noted that updates right after app launch might take longer as the system builds the app's initial view hierarchy. Optimizing view body updates and reducing unnecessary updates can enhance performance and improve startup times. Optimize SwiftUI performance with Instruments (15:10)

3. Debugging and Performance Tools: The session "What’s new in Xcode 16" highlights the use of Instruments to diagnose performance problems, including slow app launches. The Time Profiler instrument can visualize CPU usage and help identify long hangs during app launch. The new flame graph feature provides a high-level overview of trace execution, aiding in pinpointing performance bottlenecks. What’s new in Xcode 16 (09:10)

These sessions provide insights into tools and strategies for optimizing app startup time, leveraging Xcode's recommendations, and using Instruments for performance analysis.