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

@EnvironmentObject

in new code — migrate to

@Observable

Putting async work directly in
```
body
```
or
```
init
```
— use
```
.task {}
```
or explicit load methods
Creating view models as
```
@State
```
inside child views that don't own the data — pass from parent instead
Using
```
AnyView
```
type erasure — prefer
```
@ViewBuilder
```
or
```
Group
```
for conditional views
Ignoring
```
Sendable
```
requirements 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.

swiftui-patterns

NPX Install

Tags

SKILL.md Content

SwiftUI Patterns

When to Activate

State Management

Property Wrapper Selection

@Observable ViewModel

View Consuming the ViewModel

Environment Injection

View Composition

Extract Subviews to Limit Invalidation

ViewModifier for Reusable Styling

Navigation

Type-Safe NavigationStack

Performance

Use Lazy Containers for Large Collections

Stable Identifiers

Avoid Expensive Work in body

Equatable Conformance

Previews

Anti-Patterns to Avoid

References