Mode d’emploi
- Copiez la commande et examinez le paquet avant de l’installer dans votre environnement agent.
- Consultez le document original pour les outils, identifiants et environnements requis.
- Décrivez les entrées et le livrable souhaité ; comparez la sortie aux sources.
npx skills add https://github.com/affaan-m/ecc --skill swiftui-patternsAvant de commencer
- L’installation n’inclut ni abonnement au modèle, ni quota API, ni accès aux fichiers.
- Étoiles et installations reflètent l’activité, pas un test indépendant de qualité ou de sécurité.
Document Skill original
Rendu depuis le dépôt source en conservant titres, exemples, code, tableaux, liens et images.
SwiftUI Patterns
Modern SwiftUI patterns for building declarative, performant user interfaces on Apple platforms. Covers the Observation framework, view composition, type-safe navigation, and performance optimization.
When to Activate
- Building SwiftUI views and managing state (
@State,@Observable,@Binding) - Designing navigation flows with
NavigationStack - Structuring view models and data flow
- Optimizing rendering performance for lists and complex layouts
- Working with environment values and dependency injection in SwiftUI
State Management
Property Wrapper Selection
Choose the simplest wrapper that fits:
| Wrapper | Use Case |
|---|---|
@State | View-local value types (toggles, form fields, sheet presentation) |
@Binding | Two-way reference to parent's @State |
@Observable class + @State | Owned model with multiple properties |
@Observable class (no wrapper) | Read-only reference passed from parent |
@Bindable | Two-way binding to an @Observable property |
@Environment | Shared dependencies injected via .environment() |
@Observable ViewModel
Use @Observable (not ObservableObject) — it tracks property-level changes so SwiftUI only re-renders views that read the changed property:
swift
@Observable
final class ItemListViewModel {
private(set) var items: [Item] = []
private(set) var isLoading = false
var searchText = ""
private let repository: any ItemRepository
init(repository: any ItemRepository = DefaultItemRepository()) {
self.repository = repository
}
func load() async {
isLoading = true
defer { isLoading = false }
items = (try? await repository.fetchAll()) ?? []
}
}View Consuming the ViewModel
swift
struct ItemListView: View {
@State private var viewModel: ItemListViewModel
init(viewModel: ItemListViewModel = ItemListViewModel()) {
_viewModel = State(initialValue: viewModel)
}
var body: some View {
List(viewModel.items) { item in
ItemRow(item: item)
}
.searchable(text: $viewModel.searchText)
.overlay { if viewModel.isLoading { ProgressView() } }
.task { await viewModel.load() }
}
}Environment Injection
Replace @EnvironmentObject with @Environment:
swift
// Inject
ContentView()
.environment(authManager)
// Consume
struct ProfileView: View {
@Environment(AuthManager.self) private var auth
var body: some View {
Text(auth.currentUser?.name ?? "Guest")
}
}View Composition
Extract Subviews to Limit Invalidation
Break views into small, focused structs. When state changes, only the subview reading that state re-renders:
swift
struct OrderView: View {
@State private var viewModel = OrderViewModel()
var body: some View {
VStack {
OrderHeader(title: viewModel.title)
OrderItemList(items: viewModel.items)
OrderTotal(total: viewModel.total)
}
}
}ViewModifier for Reusable Styling
swift
struct CardModifier: ViewModifier {
func body(content: Content) -> some View {
content
.padding()
.background(.regularMaterial)
.clipShape(RoundedRectangle(cornerRadius: 12))
}
}
extension View {
func cardStyle() -> some View {
modifier(CardModifier())
}
}Navigation
Type-Safe NavigationStack
Use NavigationStack with NavigationPath for programmatic, type-safe routing:
swift
@Observable
final class Router {
var path = NavigationPath()
func navigate(to destination: Destination) {
path.append(destination)
}
func popToRoot() {
path = NavigationPath()
}
}
enum Destination: Hashable {
case detail(Item.ID)
case settings
case profile(User.ID)
}
struct RootView: View {
@State private var router = Router()
var body: some View {
NavigationStack(path: $router.path) {
HomeView()
.navigationDestination(for: Destination.self) { dest in
switch dest {
case .detail(let id): ItemDetailView(itemID: id)
case .settings: SettingsView()
case .profile(let id): ProfileView(userID: id)
}
}
}
.environment(router)
}
}Performance
Use Lazy Containers for Large Collections
LazyVStack and LazyHStack create views only when visible:
swift
ScrollView {
LazyVStack(spacing: 8) {
ForEach(items) { item in
ItemRow(item: item)
}
}
}Stable Identifiers
Always use stable, unique IDs in ForEach — avoid using array indices:
swift
// Use Identifiable conformance or explicit id
ForEach(items, id: \.stableID) { item in
ItemRow(item: item)
}Avoid Expensive Work in body
- Never perform I/O, network calls, or heavy computation inside
body - Use
.task {}for async work — it cancels automatically when the view disappears - Use
.sensoryFeedback()and.geometryGroup()sparingly in scroll views - Minimize
.shadow(),.blur(), and.mask()in lists — they trigger offscreen rendering
Equatable Conformance
For views with expensive bodies, conform to Equatable to skip unnecessary re-renders:
swift
struct ExpensiveChartView: View, Equatable {
let dataPoints: [DataPoint] // DataPoint must conform to Equatable
static func == (lhs: Self, rhs: Self) -> Bool {
lhs.dataPoints == rhs.dataPoints
}
var body: some View {
// Complex chart rendering
}
}Previews
Use #Preview macro with inline mock data for fast iteration:
swift
#Preview("Empty state") {
ItemListView(viewModel: ItemListViewModel(repository: EmptyMockRepository()))
}
#Preview("Loaded") {
ItemListView(viewModel: ItemListViewModel(repository: PopulatedMockRepository()))
}Anti-Patterns to Avoid
- Using
ObservableObject/@Published/@StateObject/@EnvironmentObjectin new code — migrate to@Observable - Putting async work directly in
bodyorinit— use.task {}or explicit load methods - Creating view models as
@Stateinside child views that don't own the data — pass from parent instead - Using
AnyViewtype erasure — prefer@ViewBuilderorGroupfor conditional views - Ignoring
Sendablerequirements when passing data to/from actors
References
See skill: swift-actor-persistence for actor-based persistence patterns. See skill: swift-protocol-di-testing for protocol-based DI and testing with Swift Testing.
