swiftui-pro

SwiftUI Pro

Write and review SwiftUI for correctness, modern APIs, and performance. Report real problems only — no nitpicking.

When to use

• Writing new SwiftUI views.
• Reviewing or refactoring existing SwiftUI.
• Fixing layout, state, navigation, or performance issues.

Trigger: /swiftui-pro or natural language ("review this SwiftUI view").

Core principles

• Pure SwiftUI first — only drop to UIKit when the user explicitly needs it.
• Concurrency is structured async/await; no GCD unless there's a concrete reason.
• New dependencies are a conversation, not a default — ask before adding one.
• File hygiene: one declaration per file, grouped into folders by feature.
• Language/OS target follows the project; if unset, assume the current shipping Swift and SDK rather than legacy defaults.

State management

Use @Observable (Observation framework), not ObservableObject/@Published.

❌ Legacy

final class CounterModel: ObservableObject {
    @Published var count = 0
}

struct CounterView: View {
    @StateObject private var model = CounterModel()
    var body: some View { Text("\(model.count)") }
}

✅ Modern

@Observable
final class CounterModel {
    var count = 0
}

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

Rules:

• Own the model with @State. Pass it down plainly; use @Bindable only where you need two-way bindings to its properties.
• Use @Environment for app-wide models, not singletons.

Modifiers and styling

• foregroundStyle() not foregroundColor().
• .background { ... } / .overlay { ... } closure form, not deprecated overloads.
• Prefer Grid, ViewThatFits, and layout containers over manual GeometryReader math.

❌

Text("Hi").foregroundColor(.red)

✅

Text("Hi").foregroundStyle(.red)

Navigation

Use NavigationStack with a typed path. NavigationView is deprecated.

❌

NavigationView {
    NavigationLink("Detail", destination: DetailView())
}

✅

NavigationStack(path: $path) {
    List(items) { item in
        NavigationLink(item.name, value: item.id)
    }
    .navigationDestination(for: Item.ID.self) { id in
        DetailView(id: id)
    }
}

Performance

• Use LazyVStack/LazyHStack inside ScrollView for long content; plain VStack renders everything eagerly.
• Give ForEach stable identity (Identifiable or id:), never array indices for mutable collections.
• Keep body cheap. Move expensive work out of body into the model or .task.

❌ Index identity on a mutable list

ForEach(0..<items.count, id: \.self) { i in Row(items[i]) }

✅

ForEach(items) { item in Row(item) }

Async work

Use .task (auto-cancelled on disappear), not onAppear { Task { } }.

✅

.task { await model.load() }

Accessibility (always)

• Support Dynamic Type — avoid fixed font sizes; use semantic .font(.body) etc.
• Provide .accessibilityLabel for icon-only controls.
• Respect Reduce Motion for animations.

Common mistakes checklist

• Using ObservableObject/@Published instead of @Observable.
• foregroundColor / NavigationView / other deprecated APIs.
• VStack where LazyVStack is needed.
• ForEach keyed by index on a mutable collection.
• Side effects or heavy compute in body.
• Icon-only buttons with no accessibility label.

Output format (when reviewing)

Walk the code top to bottom. For each real problem give: the file:line, a one-line statement of what's wrong, and a tight before → after snippet. Don't mention files that are already fine. Close with the two or three fixes that matter most, in priority order.