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Saurabh Dave Swift · SwiftUI · Apple Platform  ·  March 29, 2026

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Ad‑hoc frame math sprinkled through view bodies breeds flaky, non‑deterministic layout. Pull spatial rules into focused Layout types to get deterministic sizing and easier tests.

• Centralize placement math behind a small Layout so you can call sizeThatFits in XCTest and assert behavior across rotations or Dynamic Type changes.
• Use a minimal Cache inside the Layout to avoid repeated expensive measurements; document what invalidates it (for example: content changes, \.sizeCategory, or orientation).
• Combine custom Layout with LazyVStack/LazyHStack for large collections to avoid measuring every child eagerly.
• Instrument sizeThatFits and placeSubviews with Instruments or runtime timing (or OSSignposter) during rollout to spot hot paths.

When screens include large UIKit surfaces or third‑party UIViews, prefer incremental embedding with UIHostingController rather than rewriting everything at once.

What tradeoff surprised you most when adopting Layout, or how have you handled cache invalidation and flaky measurements migrating UIKit screens into SwiftUI? Share a concrete example.

#SwiftUI #iOSDev #MobileArchitecture #iOS #Swift