swiftui-expert

name	SwiftUI Expert
description	Build clean, performant, accessible SwiftUI views.

SwiftUI Expert

Build declarative iOS UIs with correct state flow and smooth animations.

State management

Pick the right property wrapper:

• @State — local, view-owned, value-type state.
• @Binding — a two-way reference to state owned elsewhere.
• @Observable (Observation framework) — model objects; views observe only the properties they read.
• @Environment — dependency injection down the tree.

@Observable final class CounterModel { var count = 0 }

struct CounterView: View {
  @State private var model = CounterModel()
  var body: some View {
    Button("Count: \(model.count)") { model.count += 1 }
  }
}

View composition

• Keep body small; extract subviews for reuse and to scope invalidation.
• Pass minimal data into subviews so only the affected views re-render.
• Use @ViewBuilder helpers instead of giant nested closures.

Animations

• Drive animation from state: withAnimation { model.expanded.toggle() }.
• Prefer .animation(_:value:) scoped to a specific value over implicit global animations.
• Use matchedGeometryEffect for shared-element transitions; transition for insert/remove.

Lists and performance

• Use LazyVStack/List for large collections so rows render on demand.
• Give items stable ids; unstable ids cause flicker and lost state.
• Avoid heavy work in body; compute in the model.

Accessibility

• Add accessibilityLabel/accessibilityValue; group related elements with accessibilityElement(children:).
• Respect Dynamic Type — use system fonts and avoid fixed frames that clip text.
• Support reduceMotion and sufficient contrast.

Rules

• Never mutate state during body evaluation — it loops or warns.
• Do async work in .task {}, which cancels on disappear, not onAppear + Task.
• Keep models testable and free of view types.

Edge cases

• Long-lived state: lift it above the view that can disappear, or it resets.
• Keyboard avoidance and safe areas: use safeAreaInset and scrollDismissesKeyboard.
• Previews: use sample data and multiple #Previews for states and Dynamic Type sizes.