Extensions & Widgets API Reference

Overview

This skill provides comprehensive API reference for Apple's widget and extension ecosystem:

• Standard Widgets (iOS 14+) — Home Screen, Lock Screen, StandBy widgets

• Interactive Widgets (iOS 17+) — Buttons and toggles with App Intents

• Live Activities (iOS 16.1+) — Real-time updates on Lock Screen and Dynamic Island

• Control Center Widgets (iOS 18+) — System-wide quick controls

• Liquid Glass Widgets (iOS 26+) — Accented rendering, glass effects, container backgrounds

• visionOS Widgets (visionOS 2+) — Mounting styles, textures, proximity awareness

• App Extensions — Shared data, lifecycle, entitlements

Widgets are SwiftUI archived snapshots rendered on a timeline by the system. Extensions are sandboxed executables bundled with your app.

When to Use This Skill

✅ Use this skill when:

• Implementing any type of widget (Home Screen, Lock Screen, StandBy)

• Creating Live Activities for ongoing events

• Building Control Center controls

• Sharing data between app and extensions

• Understanding widget timelines and refresh policies

• Integrating widgets with App Intents

• Adopting Liquid Glass rendering in widgets

• Supporting watchOS or visionOS widgets

• Implementing visionOS mounting styles, textures, or proximity awareness

❌ Do NOT use this skill for:

• Pure App Intents questions (use app-intents-ref skill)

• SwiftUI layout issues (use swiftui-layout skill)

• Performance optimization (use swiftui-performance skill)

• Debugging crashes (use xcode-debugging skill)

Related Skills

• app-intents-ref — App Intents for interactive widgets and configuration

• swift-concurrency — Async/await patterns for widget data loading

• swiftui-performance — Optimizing widget rendering

• swiftui-layout — Complex widget layouts

• extensions-widgets — Discipline skill with anti-patterns and debugging

Key Terminology

• Timeline — Series of entries defining when/what content to display; system shows entries at specified times

• TimelineProvider — Protocol supplying timeline entries (placeholder, snapshot, timeline generation)

• TimelineEntry — Struct with widget data + display date

• Timeline Budget — Daily limit (40-70) for timeline reloads

• Budget-Exempt — Reloads that don't count (user-initiated, app foregrounding, system-initiated)

• Widget Family — Size/shape (systemSmall, systemMedium, accessoryCircular, etc.)

• App Groups — Entitlement for shared data container between app and extensions

• ActivityAttributes — Static data (set once) + dynamic ContentState (updated during lifecycle)

• ContentState — Changing part of ActivityAttributes; must be under 4KB total

• Dynamic Island — iPhone 14 Pro+ Live Activity display; compact, minimal, and expanded sizes

• ControlWidget — iOS 18+ widgets for Control Center, Lock Screen, and Action Button

• Supplemental Activity Families — Enables Live Activities on Apple Watch or CarPlay

Part 1: Standard Widgets (iOS 14+)

Widget Configuration Types

StaticConfiguration

For widgets that don't require user configuration.

@main struct MyWidget: Widget { let kind: String = "MyWidget"

var body: some WidgetConfiguration {
    StaticConfiguration(kind: kind, provider: Provider()) { entry in
        MyWidgetEntryView(entry: entry)
    }
    .configurationDisplayName("My Widget")
    .description("This widget displays...")
    .supportedFamilies([.systemSmall, .systemMedium, .systemLarge])
}

}

AppIntentConfiguration (iOS 17+)

For widgets with user configuration using App Intents.

struct MyConfigurableWidget: Widget { let kind: String = "MyConfigurableWidget"

var body: some WidgetConfiguration {
    AppIntentConfiguration(
        kind: kind,
        intent: SelectProjectIntent.self,
        provider: Provider()
    ) { entry in
        MyWidgetEntryView(entry: entry)
    }
    .configurationDisplayName("Project Status")
    .description("Shows your selected project")
}

}

Migration from IntentConfiguration: iOS 16 and earlier used IntentConfiguration with SiriKit intents. Migrate to AppIntentConfiguration for iOS 17+.

ActivityConfiguration

For Live Activities (covered in Live Activities section).

Choosing the Right Configuration

No user configuration needed? Use StaticConfiguration . Simple static options? Use AppIntentConfiguration with WidgetConfigurationIntent . Dynamic options from app data? Use AppIntentConfiguration

• EntityQuery .

Quick Reference:

• StaticConfiguration — No customization (weather, battery status)

• AppIntentConfiguration (simple) — Fixed options (timer presets, theme selection)

• AppIntentConfiguration (EntityQuery) — Dynamic list from app data (project/contact/playlist picker)

• ActivityConfiguration — Live ongoing events (delivery tracking, workout progress, sports scores)

Widget Families

System Families (Home Screen)

• systemSmall (~170×170, iOS 14+) — Single piece of info, icon

• systemMedium (~360×170, iOS 14+) — Multiple data points, chart

• systemLarge (~360×380, iOS 14+) — Detailed view, list

• systemExtraLarge (~720×380, iOS 15+ iPad only) — Rich layouts, multiple views

Accessory Families (Lock Screen, iOS 16+)

• accessoryCircular (~48×48pt) — Circular complication, icon or gauge

• accessoryRectangular (~160×72pt) — Above clock, text + icon

• accessoryInline (single line) — Above date, text only

Example: Supporting Multiple Families

struct MyWidget: Widget { var body: some WidgetConfiguration { StaticConfiguration(kind: "MyWidget", provider: Provider()) { entry in if #available(iOSApplicationExtension 16.0, *) { switch entry.family { case .systemSmall: SmallWidgetView(entry: entry) case .systemMedium: MediumWidgetView(entry: entry) case .accessoryCircular: CircularWidgetView(entry: entry) case .accessoryRectangular: RectangularWidgetView(entry: entry) default: Text("Unsupported") } } else { LegacyWidgetView(entry: entry) } } .supportedFamilies([ .systemSmall, .systemMedium, .accessoryCircular, .accessoryRectangular ]) } }

Timeline System

TimelineProvider Protocol

Provides entries that define when the system should render your widget.

struct Provider: TimelineProvider { // Placeholder while loading func placeholder(in context: Context) -> SimpleEntry { SimpleEntry(date: Date(), emoji: "😀") }

// Shown in widget gallery
func getSnapshot(in context: Context, completion: @escaping (SimpleEntry) -> ()) {
    let entry = SimpleEntry(date: Date(), emoji: "📷")
    completion(entry)
}

// Actual timeline
func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> ()) {
    var entries: [SimpleEntry] = []
    let currentDate = Date()

    // Create entry every hour for 5 hours
    for hourOffset in 0 ..< 5 {
        let entryDate = Calendar.current.date(byAdding: .hour, value: hourOffset, to: currentDate)!
        let entry = SimpleEntry(date: entryDate, emoji: "⏰")
        entries.append(entry)
    }

    let timeline = Timeline(entries: entries, policy: .atEnd)
    completion(timeline)
}

}

TimelineReloadPolicy

Controls when the system requests a new timeline:

• .atEnd — Reload after last entry

• .after(date) — Reload at specific date

• .never — No automatic reload (manual only)

Manual Reload

import WidgetKit

// Reload all widgets of this kind WidgetCenter.shared.reloadAllTimelines()

// Reload specific kind WidgetCenter.shared.reloadTimelines(ofKind: "MyWidget")

Performance & Budget Quick Reference

Timeline Refresh Budget

• Daily budget: 40-70 reloads/day (varies by system load and engagement)

• Budget-exempt: User-initiated reload, app foregrounding, widget added, system reboot

• Strategic (4x/hour) — ~48 reloads/day, low battery impact

• Aggressive (12x/hour) — Budget exhausted by 6 PM, high impact

• On-demand only — 5-10 reloads/day, minimal impact

• Reload on significant data changes and time-based events. Avoid speculative or cosmetic reloads.

// ✅ GOOD: Strategic intervals (15-60 min) let entries = (0..<8).map { offset in let date = Calendar.current.date(byAdding: .minute, value: offset * 15, to: now)! return SimpleEntry(date: date, data: data) }

Memory Limits

• ~30MB for standard widgets, ~50MB for Live Activities — system terminates if exceeded

• Load only what you need (e.g., loadRecentItems(limit: 10) , not entire database)

Network Requests

Never make network requests in widget views — they won't complete before rendering. Fetch data in getTimeline() instead.

Timeline Generation

Complete getTimeline() in under 5 seconds. Cache expensive computations in the main app, read pre-computed data from shared container, limit to 10-20 entries.

View Rendering

Precompute everything in TimelineEntry , keep views simple. No expensive operations in body .

Images

• Use asset catalog images or SF Symbols (fast)

• Small images from shared container are acceptable

• AsyncImage does NOT work in widgets

• Large images cause memory termination

Part 2: Interactive Widgets (iOS 17+)

Button and Toggle

Interactive widgets use SwiftUI Button and Toggle with App Intents.

Button with App Intent

Button(intent: IncrementIntent()) { Label("Increment", systemImage: "plus.circle") }

The intent updates shared data via App Groups in its perform() method. See axiom-app-intents-ref for full AppIntent definition syntax.

Toggle with App Intent

Same pattern as Button — use a Toggle bound to state, invoke intent on change:

Toggle(isOn: $isEnabled) { Text("Feature") } .onChange(of: isEnabled) { newValue in Task { try? await ToggleFeatureIntent(enabled: newValue).perform() } }

The intent follows the same AppIntent structure with a @Parameter(title: "Enabled") var enabled: Bool . See axiom-app-intents-ref for full AppIntent definition syntax.

invalidatableContent Modifier

Provides visual feedback during App Intent execution.

struct MyWidgetView: View { var entry: Provider.Entry

var body: some View {
    VStack {
        Text(entry.status)
            .invalidatableContent() // Dims during intent execution

        Button(intent: RefreshIntent()) {
            Image(systemName: "arrow.clockwise")
        }
    }
}

}

Effect: Content with .invalidatableContent() becomes slightly transparent while the associated intent executes, providing user feedback.

Animation System

contentTransition for Numeric Text

Text("(entry.value)") .contentTransition(.numericText(value: Double(entry.value)))

Effect: Numbers smoothly count up or down instead of instantly changing.

View Transitions

VStack { if entry.showDetail { DetailView() .transition(.scale.combined(with: .opacity)) } } .animation(.spring(response: 0.3), value: entry.showDetail)

Part 3: Configurable Widgets (iOS 17+)

WidgetConfigurationIntent

Define configuration parameters for your widget.

import AppIntents

struct SelectProjectIntent: WidgetConfigurationIntent { static var title: LocalizedStringResource = "Select Project" static var description = IntentDescription("Choose which project to display")

@Parameter(title: "Project")
var project: ProjectEntity?

// Provide default value
static var parameterSummary: some ParameterSummary {
    Summary("Show \(\.$project)")
}

}

Entity and EntityQuery

Provide dynamic options for configuration.

struct ProjectEntity: AppEntity { var id: String var name: String

static var typeDisplayRepresentation = TypeDisplayRepresentation(name: "Project")

var displayRepresentation: DisplayRepresentation {
    DisplayRepresentation(title: "\(name)")
}

}

struct ProjectQuery: EntityQuery { func entities(for identifiers: [String]) async throws -> [ProjectEntity] { // Return projects matching these IDs return await ProjectStore.shared.projects(withIDs: identifiers) }

func suggestedEntities() async throws -> [ProjectEntity] {
    // Return all available projects
    return await ProjectStore.shared.allProjects()
}

}

Using Configuration in Provider

struct Provider: AppIntentTimelineProvider { func timeline(for configuration: SelectProjectIntent, in context: Context) async -> Timeline<SimpleEntry> { let project = configuration.project // Use selected project let entries = await generateEntries(for: project) return Timeline(entries: entries, policy: .atEnd) } }

Part 4: Live Activities (iOS 16.1+)

ActivityAttributes

Defines static and dynamic data for a Live Activity.

import ActivityKit

struct PizzaDeliveryAttributes: ActivityAttributes { // Static data - set when activity starts, never changes struct ContentState: Codable, Hashable { // Dynamic data - updated throughout activity lifecycle var status: DeliveryStatus var estimatedDeliveryTime: Date var driverName: String? }

// Static attributes
var orderNumber: String
var pizzaType: String

}

Key constraint: ActivityAttributes total data size must be under 4KB to start successfully.

Starting Activities

Request Authorization

import ActivityKit

let authorizationInfo = ActivityAuthorizationInfo() let areActivitiesEnabled = authorizationInfo.areActivitiesEnabled

Start an Activity

let attributes = PizzaDeliveryAttributes( orderNumber: "12345", pizzaType: "Pepperoni" )

let initialState = PizzaDeliveryAttributes.ContentState( status: .preparing, estimatedDeliveryTime: Date().addingTimeInterval(30 * 60) )

let activity = try Activity.request( attributes: attributes, content: ActivityContent(state: initialState, staleDate: nil), pushType: nil // or .token for push notifications )

Error Handling

Common Activity Errors

Always check ActivityAuthorizationInfo().areActivitiesEnabled before requesting. Handle these errors from Activity.request() :

• ActivityAuthorizationError — User denied Live Activities permission

• ActivityError.dataTooLarge — ActivityAttributes exceeds 4KB; reduce attribute size

• ActivityError.tooManyActivities — System limit reached (typically 2-3 simultaneous)

Store activity.id after successful request for later updates.

Updating Activities

Update with New Content

// Find active activity by stored ID guard let activity = Activity<PizzaDeliveryAttributes>.activities .first(where: { $0.id == storedActivityID }) else { return }

let updatedState = PizzaDeliveryAttributes.ContentState( status: .onTheWay, estimatedDeliveryTime: Date().addingTimeInterval(10 * 60), driverName: "John" )

await activity.update( ActivityContent( state: updatedState, staleDate: Date().addingTimeInterval(60) // Mark stale after 1 min ) )

Alert Configuration

await activity.update(updatedContent, alertConfiguration: AlertConfiguration( title: "Pizza is here!", body: "Your (attributes.pizzaType) pizza has arrived", sound: .default ))

Monitoring Activity Lifecycle

Use activity.activityStateUpdates async sequence to observe state changes (.active , .ended , .dismissed , .stale ). Clean up stored activity IDs on .ended or .dismissed . Cancel the monitoring task in deinit .

Ending Activities

Dismissal Policies

await activity.end( ActivityContent(state: finalState, staleDate: nil), dismissalPolicy: .default )

Dismissal policy options:

• .immediate — Removes instantly

• .default — Stays on Lock Screen for ~4 hours

• .after(date) — Removes at specific time (e.g., .after(Date().addingTimeInterval(3600)) )

Push Notifications for Live Activities

Request Push Token

let activity = try Activity.request( attributes: attributes, content: initialContent, pushType: .token // Request push token )

// Monitor for push token for await pushToken in activity.pushTokenUpdates { let tokenString = pushToken.map { String(format: "%02x", $0) }.joined() // Send to your server await sendTokenToServer(tokenString, activityID: activity.id) }

Frequent Push Updates (iOS 18.2+)

Standard limit is ~10-12 pushes/hour. For live events (sports, stocks), add the com.apple.developer.activity-push-notification-frequent-updates entitlement for significantly higher limits.

Part 5: Dynamic Island (iOS 16.1+)

Presentation Types

Live Activities appear in the Dynamic Island with three size classes:

Compact (Leading + Trailing)

Shown when another Live Activity is expanded or when multiple activities are active.

DynamicIsland { DynamicIslandExpandedRegion(.leading) { Image(systemName: "timer") } DynamicIslandExpandedRegion(.trailing) { Text("(entry.timeRemaining)") } // ... } compactLeading: { Image(systemName: "timer") } compactTrailing: { Text("(entry.timeRemaining)") .frame(width: 40) }

Minimal

Shown when more than two Live Activities are active (circular avatar).

DynamicIsland { // ... } minimal: { Image(systemName: "timer") .foregroundStyle(.tint) }

Expanded

Shown when user long-presses the compact view.

DynamicIsland { DynamicIslandExpandedRegion(.leading) { Image(systemName: "timer") .font(.title) }

DynamicIslandExpandedRegion(.trailing) {
    VStack(alignment: .trailing) {
        Text("\(entry.timeRemaining)")
            .font(.title2.monospacedDigit())
        Text("remaining")
            .font(.caption)
    }
}

DynamicIslandExpandedRegion(.center) {
    // Optional center content
}

DynamicIslandExpandedRegion(.bottom) {
    HStack {
        Button(intent: PauseIntent()) {
            Label("Pause", systemImage: "pause.fill")
        }
        Button(intent: StopIntent()) {
            Label("Stop", systemImage: "stop.fill")
        }
    }
}

}

Design Principles (From WWDC 2023-10194)

Concentric Alignment

Content should nest concentrically inside the Dynamic Island's rounded shape with even margins. Use Circle() or RoundedRectangle(cornerRadius:) — never sharp Rectangle() which pokes into corners.

Biological Motion

Dynamic Island animations should feel organic and elastic. Use .spring(response: 0.6, dampingFraction: 0.7) or .interpolatingSpring(stiffness: 300, damping: 25) instead of linear animations.

Part 6: Control Center Widgets (iOS 18+)

ControlWidget Protocol

Controls appear in Control Center, Lock Screen, and Action Button (iPhone 15 Pro+).

StaticControlConfiguration

For simple controls without configuration.

import WidgetKit import AppIntents

struct TorchControl: ControlWidget { var body: some ControlWidgetConfiguration { StaticControlConfiguration(kind: "TorchControl") { ControlWidgetButton(action: ToggleTorchIntent()) { Label("Flashlight", systemImage: "flashlight.on.fill") } } .displayName("Flashlight") .description("Toggle flashlight") } }

AppIntentControlConfiguration

For configurable controls.

struct TimerControl: ControlWidget { var body: some ControlWidgetConfiguration { AppIntentControlConfiguration( kind: "TimerControl", intent: ConfigureTimerIntent.self ) { configuration in ControlWidgetButton(action: StartTimerIntent(duration: configuration.duration)) { Label("(configuration.duration)m Timer", systemImage: "timer") } } } }

ControlWidgetButton

For discrete actions (one-shot operations).

ControlWidgetButton(action: PlayMusicIntent()) { Label("Play", systemImage: "play.fill") } .tint(.purple)

ControlWidgetToggle

For boolean state.

struct AirplaneModeControl: ControlWidget { var body: some ControlWidgetConfiguration { StaticControlConfiguration(kind: "AirplaneModeControl") { ControlWidgetToggle( isOn: AirplaneModeIntent.isEnabled, action: AirplaneModeIntent() ) { isOn in Label(isOn ? "On" : "Off", systemImage: "airplane") } } } }

Value Providers (Async State)

For controls needing async state, pass a ControlValueProvider to StaticControlConfiguration :

struct ThermostatProvider: ControlValueProvider { func currentValue() async throws -> ThermostatValue { let temp = try await HomeManager.shared.currentTemperature() return ThermostatValue(temperature: temp) } var previewValue: ThermostatValue { ThermostatValue(temperature: 72) } }

The provider value is passed to your control's closure: { value in ControlWidgetButton(...) } .

Configurable Controls

Use AppIntentControlConfiguration with a WidgetConfigurationIntent (same pattern as configurable widgets). Add .promptsForUserConfiguration() to show configuration UI when the user adds the control.

Control Refinements

• .controlWidgetActionHint("Toggles flashlight") — VoiceOver accessibility hint

• .displayName("My Control") / .description("...") — Shown in Control Center UI

Part 7: iOS 18+ Updates

Accented Rendering and Liquid Glass

Widget rendering modes span multiple iOS versions: widgetAccentable() (iOS 16+), WidgetAccentedRenderingMode (iOS 18+), and Liquid Glass effects like glassEffect() and GlassEffectContainer (iOS 26+). Detect the mode and adapt layout accordingly.

Detecting Rendering Mode

struct MyWidgetView: View { @Environment(.widgetRenderingMode) var renderingMode

var body: some View {
    if renderingMode == .accented {
        // Simplified layout — opaque images tinted white, background replaced with glass
    } else {
        // Standard full-color layout
    }
}

}

widgetAccentable(_:)

Marks views as part of the accent group. In accented mode, accent-group views are tinted separately from primary-group views, creating visual hierarchy.

HStack { VStack(alignment: .leading) { Text("Title") .font(.headline) .widgetAccentable() // Accent group — tinted in accented mode Text("Subtitle") // Primary group by default } Image(systemName: "star.fill") .widgetAccentable() // Also accent group }

WidgetAccentedRenderingMode

Controls how images render in accented mode. Apply to Image views:

Image("myPhoto") .widgetAccentedRenderingMode(.accented) // Tinted with accent color Image("myIcon") .widgetAccentedRenderingMode(.monochrome) // Rendered as monochrome Image("myBadge") .widgetAccentedRenderingMode(.fullColor) // Keeps original colors (opt-out)

Best practices: Display full-color images only in .fullColor rendering mode. Use .widgetAccentable() strategically for visual hierarchy. Test with multiple accent colors and background images.

Container Backgrounds

VStack { /* content */ } .containerBackground(for: .widget) { Color.blue.opacity(0.2) }

In accented mode, the system removes the background and replaces it with themed glass. To prevent removal (excludes widget from iPad Lock Screen, StandBy):

.containerBackgroundRemovable(false)

Liquid Glass in Custom Widget Elements

Text("Label") .padding() .glassEffect() // Default capsule shape

Image(systemName: "star.fill") .frame(width: 60, height: 60) .glassEffect(.regular, in: .rect(cornerRadius: 12))

Button("Action") { } .buttonStyle(.glass)

Combine multiple glass elements with GlassEffectContainer :

GlassEffectContainer(spacing: 20.0) { HStack(spacing: 20.0) { Image(systemName: "cloud") .frame(width: 60, height: 60) .glassEffect() Image(systemName: "sun") .frame(width: 60, height: 60) .glassEffect() } }

Cross-Platform Support

visionOS Widgets (visionOS 2+)

visionOS widgets are 3D objects placed in physical space — mounted on surfaces or floating. They support unique spatial features.

Mounting Styles

Widgets can be elevated (on top of surfaces) or recessed (embedded into vertical surfaces like walls):

.supportedMountingStyles([.elevated, .recessed]) // Default is both // .supportedMountingStyles([.recessed]) // Wall-only widget

If limited to .recessed , users cannot place the widget on horizontal surfaces.

Widget Textures

Two visual textures for spatial appearance:

.widgetTexture(.glass) // Default — transparent glass-like appearance .widgetTexture(.paper) // Poster-like look, effective with extra-large sizes

Proximity Awareness (levelOfDetail)

Widgets adapt to user distance automatically. The system animates transitions between detail levels:

@Environment(.levelOfDetail) var levelOfDetail

var body: some View { VStack { Text(entry.value) .font(levelOfDetail == .simplified ? .largeTitle : .title) } }

Values: .default (close viewing) and .simplified (distance viewing — use larger text, fewer details).

visionOS Widget Families

visionOS supports all system families plus extra-large sizes:

.supportedFamilies([ .systemSmall, .systemMedium, .systemLarge, .systemExtraLarge, .systemExtraLargePortrait // visionOS-specific portrait orientation ])

Extra-large families are particularly effective with .widgetTexture(.paper) for poster-like displays.

Background Detection

Detect whether the widget background is visible (removed in accented mode):

@Environment(.showsWidgetContainerBackground) var showsBackground

CarPlay (iOS 18+)

Add .supplementalActivityFamilies([.medium]) to ActivityConfiguration . Uses StandBy-style full-width dashboard presentation.

macOS Menu Bar

Live Activities from paired iPhone appear automatically in macOS Sequoia+ menu bar. No code changes required.

watchOS Controls (11+)

ControlWidget works identically on watchOS — available in Control Center, Action Button, and Smart Stack. Same StaticControlConfiguration / ControlWidgetButton pattern as iOS.

Relevance Widgets (iOS 18+)

Use .relevanceConfiguration(for:score:attributes:) to help the system promote widgets in Smart Stack. Attributes include .location(CLLocation) , .timeOfDay(DateInterval) , and .activity(String) for context-aware ranking.

Push Notification Updates (iOS 18+)

Implement PKPushRegistryDelegate and handle .widgetKit push type to receive server-to-widget pushes. Update shared container data and call WidgetCenter.shared.reloadAllTimelines() . Pushes to iPhone automatically sync to Apple Watch and CarPlay.

Part 8: App Groups & Data Sharing

App Groups Entitlement

Required for sharing data between your app and extensions.

Configuration

• Xcode: Targets → Signing & Capabilities → Add "App Groups"

• Identifier format: group.com.company.appname

• Enable for BOTH main app target AND extension target

Shared Containers

Access Shared Container

let sharedContainer = FileManager.default.containerURL( forSecurityApplicationGroupIdentifier: "group.com.mycompany.myapp" )!

let dataFileURL = sharedContainer.appendingPathComponent("widgetData.json")

UserDefaults with App Groups

// Main app - write data let shared = UserDefaults(suiteName: "group.com.mycompany.myapp")! shared.set("Updated value", forKey: "myKey")

// Widget extension - read data let shared = UserDefaults(suiteName: "group.com.mycompany.myapp")! let value = shared.string(forKey: "myKey")

Core Data with App Groups

Point NSPersistentStoreDescription at the shared container URL:

let sharedStoreURL = FileManager.default.containerURL( forSecurityApplicationGroupIdentifier: "group.com.mycompany.myapp" )!.appendingPathComponent("MyApp.sqlite")

let description = NSPersistentStoreDescription(url: sharedStoreURL) container.persistentStoreDescriptions = [description]

IPC Communication

• Background URL Session — Set config.sharedContainerIdentifier to your App Group ID for downloads accessible by extensions

• Darwin Notification Center — Use CFNotificationCenterPostNotification / CFNotificationCenterAddObserver with CFNotificationCenterGetDarwinNotifyCenter() for simple cross-process signals (e.g., notify widget to call WidgetCenter.shared.reloadAllTimelines() )

Part 9: watchOS Integration

supplementalActivityFamilies (watchOS 11+)

Add .supplementalActivityFamilies([.small]) to ActivityConfiguration to show Live Activities on Apple Watch Smart Stack (same modifier used for CarPlay with .medium ).

activityFamily Environment

Use @Environment(.activityFamily) to adapt layout — check for .small (watchOS) vs iPhone layout.

Always On Display

Use @Environment(.isLuminanceReduced) to simplify views for Always On Display — reduce detail, use white text, larger fonts. Combine with @Environment(.colorScheme) for proper dark mode handling.

Update Budgeting (watchOS)

watchOS updates sync automatically with iPhone via push notifications. Updates may be delayed if watch is out of Bluetooth range.

Part 10: Practical Workflows

Building Your First Widget

For a complete step-by-step tutorial with working code examples, see Apple's Building Widgets Using WidgetKit and SwiftUI sample project.

Key steps: Add widget extension target, configure App Groups, implement TimelineProvider, design SwiftUI view, update from main app. See Expert Review Checklist below for production requirements.

Expert Review Checklist

Before Shipping Widgets

Architecture:

• App Groups entitlement configured in app AND extension

• Group identifier matches exactly in both targets

• Shared container used for ALL data sharing

• No UserDefaults.standard in widget code

Performance:

• Timeline generation completes in < 5 seconds

• No network requests in widget views

• Timeline has reasonable refresh intervals (≥ 15 min)

• Entry count reasonable (< 20-30 entries)

• Memory usage under limits (~30MB widgets, ~50MB activities)

• Images optimized (asset catalog or SF Symbols preferred)

Data & State:

• Widget handles missing/nil data gracefully

• Entry dates in chronological order

• Placeholder view looks reasonable

• Snapshot view representative of actual use

User Experience:

• Widget appears in widget gallery

• configurationDisplayName clear and concise

• description explains widget purpose

• All supported families tested and look correct

• Text readable on both light and dark backgrounds

• Interactive elements (buttons/toggles) work correctly

Live Activities (if applicable):

• ActivityAttributes under 4KB

• Authorization checked before starting

• Activity ends when event completes

• Proper dismissal policy set

• watchOS support configured if relevant (supplementalActivityFamilies)

• Dynamic Island layouts tested (compact, minimal, expanded)

Liquid Glass (if applicable):

• widgetAccentable() applied for visual hierarchy in accented mode

• WidgetAccentedRenderingMode set on images (.accented , .monochrome , or .fullColor )

• Tested with multiple accent colors and background images

• Container background configured with .containerBackground(for: .widget)

visionOS (if applicable):

• Mounting styles configured (.elevated , .recessed , or both)

• Widget texture chosen (.glass or .paper )

• levelOfDetail handled for proximity-aware layouts

• Extra-large families supported if appropriate (.systemExtraLarge , .systemExtraLargePortrait )

• Tested at different distances for proximity transitions

Control Center Widgets (if applicable):

• ControlValueProvider async and fast (< 1 second)

• previewValue provides reasonable fallback

• displayName and description set

• Tested in Control Center, Lock Screen, Action Button

Testing:

• Tested on actual device (not just simulator)

• Tested adding/removing widget

• Tested app data changes → widget updates

• Tested force-quit app → widget still works

• Tested low memory scenarios

• Tested all iOS versions you support

• Tested with no internet connection

Testing Guidance

Unit Testing Pattern

Test placeholder() , getSnapshot() , and getTimeline() methods. Save test data to shared container, call getTimeline() with a mock context, assert entries are non-empty and contain expected data. Use waitForExpectations(timeout: 5.0) for async timeline generation.

Manual Testing Checklist

• Add widget to Home Screen, verify widget gallery, all supported sizes, data matches app

• Change data in main app, observe widget updates, force-quit app, reboot device

• Delete all app data (graceful handling), disable network (offline), Low Power Mode, multiple instances

• Monitor memory in Xcode Debug Navigator, check timeline generation time in Console, test on older devices

Debugging Tips

• Add print() logging in getTimeline() to verify it's being called and data is loaded

• Verify App Groups: print FileManager.default.containerURL(forSecurityApplicationGroupIdentifier:) in both app and widget — paths must match

• After data changes in main app, call WidgetCenter.shared.reloadAllTimelines()

Part 11: Troubleshooting

Widget not appearing in gallery: Check WidgetBundle includes it, verify supportedFamilies() , check extension's "Skip Install" = NO, verify deployment target matches app.

Widget Not Refreshing

Symptoms: Widget shows stale data, doesn't update

Diagnostic Steps:

• Check timeline policy (.atEnd vs .after() vs .never )

• Verify you're not exceeding daily budget (40-70 reloads)

• Check if getTimeline() is being called (add logging)

• Ensure App Groups configured correctly for shared data

Solution:

// Manual reload from main app when data changes import WidgetKit

WidgetCenter.shared.reloadAllTimelines() // or WidgetCenter.shared.reloadTimelines(ofKind: "MyWidget")

Data Not Shared Between App and Widget

Symptoms: Widget shows default/empty data

Diagnostic Steps:

• Verify App Groups entitlement in BOTH targets

• Check group identifier matches exactly

• Ensure using same suiteName in both targets

• Check file path if using shared container

Solution:

// Both app AND extension must use: let shared = UserDefaults(suiteName: "group.com.mycompany.myapp")!

// NOT: let shared = UserDefaults.standard // ❌ Different containers

Live Activity Won't Start

Symptoms: Activity.request() throws error

Common Errors:

"Activity size exceeds 4KB":

// ❌ BAD: Large images in attributes struct MyAttributes: ActivityAttributes { var productImage: UIImage // Too large! }

// ✅ GOOD: Use asset catalog names struct MyAttributes: ActivityAttributes { var productImageName: String // Reference to asset }

"Activities not enabled":

// Check authorization first let authInfo = ActivityAuthorizationInfo() guard authInfo.areActivitiesEnabled else { throw ActivityError.notEnabled }

Interactive Widget Button Not Working

Symptoms: Tapping button does nothing

Diagnostic Steps:

• Verify App Intent's perform() returns IntentResult

• Check intent is imported in widget target

• Ensure button uses intent: parameter, not action:

• Check Console for intent execution errors

Solution:

// ✅ CORRECT: Use intent parameter Button(intent: MyIntent()) { Label("Action", systemImage: "star") }

// ❌ WRONG: Don't use action closure Button(action: { /* This won't work in widgets */ }) { Label("Action", systemImage: "star") }

Control Center widget slow: Use async in ControlValueProvider.currentValue() , never block with Thread.sleep . Provide fast previewValue fallback.

Widget shows wrong size: Switch on @Environment(.widgetFamily) in view, adapt layout per family, avoid hardcoded sizes.

Timeline entries out of order: Ensure entry dates are chronological. Use incrementing offsets from Date() .

watchOS Live Activity not showing: Add .supplementalActivityFamilies([.small]) to ActivityConfiguration , verify watchOS 11+, check Bluetooth/pairing.

Performance Issues

Symptoms: Widget rendering slow, battery drain

Common Causes:

• Too many timeline entries (> 100)

• Network requests in view code

• Heavy computation in getTimeline()

• Refresh intervals too frequent (< 15 min)

Solution:

// ✅ GOOD: Strategic intervals let entries = (0..<8).map { offset in let date = Calendar.current.date(byAdding: .minute, value: offset * 15, to: now)! return SimpleEntry(date: date, data: precomputedData) }

// ❌ BAD: Too frequent, too many entries let entries = (0..<100).map { offset in let date = Calendar.current.date(byAdding: .minute, value: offset, to: now)! return SimpleEntry(date: date, data: fetchFromNetwork()) // Network in timeline }

Debugging Widgets

Simulator vs Device

• Simulator: Widgets refresh immediately; no budget limits apply. Useful for layout testing but misleading for refresh behavior.

• Device: Budget-limited (40-70 reloads/day). Test on device before shipping to verify real-world refresh timing.

• Xcode Previews: Work for layout but skip getTimeline() . Test timeline logic with unit tests or device runs.

Common Debugging Workflow

• Add print() in getTimeline() — verify it's called and data loads

• Check Console.app filtered by widget extension process name

• Use WidgetCenter.shared.getCurrentConfigurations() to verify registration

• If widget shows old data after app update, verify App Groups container paths match

Data Sharing Patterns

SwiftData in Widgets (iOS 17+):

• Create ModelContainer in widget with same schema as main app

• Use shared App Groups container: ModelConfiguration(url: containerURL)

• Widget reads only — never write from widget to avoid conflicts

• Main app calls WidgetCenter.shared.reloadAllTimelines() after writes

GRDB/SQLite in Widgets:

• Share database file via App Groups container

• Use DatabasePool (not DatabaseQueue ) for concurrent reads

• Widget opens read-only connection: try DatabasePool(path: dbPath, configuration: readOnlyConfig)

• Set configuration.readonly = true in widget to prevent accidental writes

Resources

WWDC: 2025-278, 2024-10157, 2024-10068, 2024-10098, 2023-10028, 2023-10194, 2022-10184, 2022-10185

Docs: /widgetkit, /activitykit, /appintents

Skills: axiom-app-intents-ref, axiom-swift-concurrency, axiom-swiftui-performance, axiom-swiftui-layout, axiom-extensions-widgets

Version: 0.9 | Platforms: iOS 14+, iPadOS 14+, watchOS 9+, macOS 11+, visionOS 2+