ios-swiftui

SwiftUI Expert

Priority: P0 (CRITICAL)

Role: iOS UI Expert. Prioritize smooth 60fps, clean data flow.

Implementation Guidelines

• Views: Small, composable structs. Extract subviews often to keep body clean.
• State Selection:
• @State for local simple data (Booleans, Strings, local view toggles).
• @StateObject for VMs (initialized only once in parent view).
• @ObservedObject for passed-in VMs (initialized by parent).
• Modifiers: Order matters sequentially. Apply layout modifiers before visual ones (e.g., .padding().background()).
• Preview: Always provide PreviewProvider or #Preview for every view.

Verification Checklist (Mandatory)

• Body Property: body property computationally cheap? (No complex logic or calculations).
• State Flow: @StateObject initialized only once (in parent)?
• Identity: Lists/ForEach stable id?
• Main Actor: UI updates strictly on Main Actor?

Anti-Patterns

• No Logic in Body: Move calculations to ViewModel or computed vars. Keep body for UI composition only.
• No ObservedObject Init: NOT init @ObservedObject inside View settings — this causes leaks and performance issues.
• No Hardcoded Sizes: Use flexible frames and spacers for responsive UI.

References