SwiftUI vs UIKit: Performance Profiling

The Rendering Loop

SwiftUI uses a diffing algorithm on the Attribute Graph. UIKit manipulates the layer tree directly. SwiftUI is generally faster to write, but can be slower to calculate diffs on huge trees.

List vs LazyVStack

List in SwiftUI wraps UITableView (mostly). LazyVStack is pure SwiftUI. For 10,000 items, UICollectionView still reigns supreme in recycling efficiency.

Attribute Graph

Understanding how SwiftUI tracks state. Every @State change triggers a diff. Over-observing on the root view kills performance.

Memory Footprint

SwiftUI structs are lightweight (value types). UIKit classes are heavier (reference types). SwiftUI wins on static memory, but diffing allocates transient objects.

Animation Drop Frames

SwiftUI animations are offloaded to Core Animation mostly. Complex layout transitions (matchedGeometryEffect) can drop frames if the view hierarchy is too deep.

Mixing Both

Don't be afraid to wrap a UICollectionView in UIViewRepresentable if SwiftUI's list stutters. It's a valid optimization strategy.

Verdict

SwiftUI is ready for 95% of screens. For the complex 5% (feeds with video autoplay), stick to UIKit optimization techniques.