swiftui-ui-patterns

Use @State for local view-owned value state, @Binding when a child mutates parent-owned state, and @State with an @Observable type for root-owned reference models on iOS 17+. Choose the ownership location first, then pick the narrowest wrapper that fits.

Give each tab its own router object owning a path array, bind NavigationStack(path:) to it, and map routes with a single navigationDestination(for:) block. Inject the router via .environment so child views navigate without prop-drilling.

Prefer sheet(item:) when the presentation state represents a selected model, since it guarantees a single active sheet and avoids if-let inside the sheet body. Centralize multiple modals with an Identifiable SheetDestination enum.

The Observation framework requires iOS 17, so on iOS 16 fall back to ObservableObject with @StateObject for root ownership and @ObservedObject for injected models. Reserve @EnvironmentObject for truly shared app-level state.

Excessive re-renders usually come from unstable ForEach identity, expensive work inside body, or overly broad observation scope. Use stable IDs, move heavy transforms into models, and narrow which views read changing state.

Use .task for load-on-appear work and .task(id:) when work should restart for changing inputs like search queries. Treat cancellation as normal, debounce user-driven requests, and keep explicit loading and error states.