iOS SDK runtime and interaction mechanics

Overview

Use this concept document to understand how the Optimization iOS SDK runs shared optimization behavior in a native app, how SwiftUI and UIKit integrations share the same client, and how consent, state, entry resolution, tracking, preview overrides, and offline delivery work.

This document applies to native apps on iOS 15 or later and macOS 12 or later. SwiftUI and UIKit sections name runtime-specific APIs where behavior differs.

For step-by-step setup, see Integrate the Optimization iOS SDK in a SwiftUI app and Integrate the Optimization iOS SDK in a UIKit app. For the full Contentful entry contract, see Entry optimization and variant resolution.

Runtime boundary

The iOS SDK is a native Swift Package named ContentfulOptimization. Swift owns native app concerns such as persistence, networking, lifecycle handling, SwiftUI helpers, UIKit preview-panel presentation, and app-facing public APIs.

Shared optimization behavior runs inside a local JavaScriptCore context. That bridge lets the iOS SDK use the same optimization, profile, consent, and event-delivery behavior as the JavaScript SDKs while exposing a Swift API to the application.

Applications do not call the JavaScript layer directly. The public boundary is Swift:

• OptimizationClient is the main facade for initialization, state, optimization, tracking, and preview controls.
• OptimizationRoot, OptimizedEntry, OptimizationScrollView, and .trackScreen(name:) provide SwiftUI integration helpers.
• PreviewPanelViewController provides the UIKit preview-panel host.

This split also defines what the SDK does not own. The application still fetches Contentful entries, manages consent UX, controls routing, decides identity policy, and renders the final UI.

Prerequisites and runtime constraints

Decide these policies before initialization because they shape the client state the bridge receives at startup and the events it can emit before runtime consent changes:

Lifecycle and main actor

OptimizationClient has two phases:

SwiftUI apps usually let OptimizationRoot call initialize(config:). UIKit apps usually call initialize(config:) from scene or app startup before passing the client into view controllers.

OptimizationClient is @MainActor. Call it from main-thread contexts such as SwiftUI view tasks, SwiftUI event handlers, view-controller lifecycle methods, or Task { @MainActor in ... } blocks. The compiler can flag background calls as concurrency errors.

Typical apps keep one OptimizationClient alive for the app or scene lifetime. Use destroy() for test teardown or deliberate SDK reset flows.

Configuration and locale handoff

Every iOS integration builds an OptimizationConfig:

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OptimizationConfig(
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    clientId: "your-client-id",
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    environment: "main",
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    locale: "en-US",
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    logLevel: .debug
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)

Only clientId is required. environment defaults to "main". Base URL overrides belong only in integrations that need non-default Experience API or Insights API endpoints.

Use top-level locale for the SDK Experience/event locale. When the application renders localized Contentful entries, choose an app-owned Contentful locale and pass it to the app’s Contentful Delivery API request before entries are passed to OptimizedEntry or resolveOptimizedEntry(...). For the full locale model, see Locale handling in the Optimization SDK Suite.

State and persistence

OptimizationClient is an ObservableObject. It publishes runtime state that SwiftUI and UIKit code can observe:

SwiftUI code reads these values through @EnvironmentObject. UIKit code can subscribe through Combine publishers such as client.$state and client.$selectedOptimizations.

Use state.canOptimize when rendering depends on variant data being available. Use optimizationPossible when the app needs to know whether current consent and allow-list settings can produce optimization data at all. For the cross-SDK distinction, see Core state management.

Custom Flags use the same Core-backed model as the Web SDKs: client.getFlag(_:) returns the current JSON value, and client.flagPublisher(_:) returns an AnyPublisher<JSONValue?, Never> that updates on distinct value changes. Reading or subscribing to a flag can emit deduplicated flag-view events when consent and profile state allow it, so treat flag delivery as an analytics exposure.

For the lower-level state model shared through the native bridge, see Core state management.

The SDK persists consent with UserDefaults. When persistence consent is true, it also persists profile-continuity values such as profile, selected changes, selected optimizations, and the anonymous ID. StorageDefaults are startup defaults, not one-time seeds. During initialization, configured defaults take precedence over persisted SDK values, so a configured consent or persistence default can replace a visitor’s stored choice on each launch.

Use StorageDefaults(consent: true) only when the application’s policy is truly default-on at startup. If the application persists user choices in a CMP, account setting, or app preference, leave StorageDefaults.consent and StorageDefaults.persistenceConsent unset. Resolve the policy at startup and call client.consent(...) after the client is available instead of seeding a choice every launch. If the application relies on SDK consent storage, also leave those defaults unset so the persisted SDK consent can restore naturally.

When durable profile-continuity persistence is allowed, the client writes profile-continuity values to UserDefaults before publishing the corresponding state snapshot and selected optimizations. Application code and XCUITest flows can wait for SDK-derived state rather than adding storage-timing delays before relaunching.

Consent and event gates

Consent is a three-state value: true, false, or unset. Until consent is granted, the SDK blocks event types that are not allow-listed. iOS uses the native default allow-list when OptimizationConfig.allowedEventTypes is unset:

This is the default iOS/native behavior, not a universal SDK rule. allowedEventTypes replaces the default allow-list. Use allowedEventTypes: [] when no Optimization event can emit before explicit consent, or pass a custom list when policy permits specific pre-consent events. Allow-listed pre-consent events still mark context.gdpr.isConsentGiven as false until event consent is explicitly true.

Call client.consent(true) when the visitor grants consent and client.consent(false) when the visitor rejects it. Boolean consent controls both event emission and durable profile-continuity persistence by default. client.consent(false) clears event consent and persistence consent, purges SDK queues, and clears SDK-managed durable profile-continuity storage while leaving active in-memory state available until the app resets or tears down the client.

Use client.consent(events:persistence:) when event emission and durable profile continuity need separate policy decisions. For example, this call allows events while keeping profile continuity session-only:

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client.consent(events: true, persistence: false)

client.consent(events: false) withdraws event consent and purges SDK queues, but it does not clear persistence consent unless persistence: false is also passed.

Read client.state.consent for event consent and client.state.persistenceConsent for durable profile-continuity persistence consent. For cross-SDK consent guidance, see Consent management in the Optimization SDK Suite.

Entry optimization boundary

Entry optimization is a local, synchronous decision once the app has both Contentful entry data and selected optimizations.

The application provides:

• A single-locale Contentful entry dictionary.
• Linked optimization references and variant entries in the Contentful payload.
• An explicit selectedOptimizations snapshot only when the caller needs one.

The SDK returns either the baseline entry or the resolved variant entry:

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let result = client.resolveOptimizedEntry(
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    baseline: entry,
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    selectedOptimizations: client.selectedOptimizations
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)
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let resolvedEntry = result.entry
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let selectedOptimization = result.selectedOptimization

Omit selectedOptimizations when you want direct resolution to use the current bridge and client state. Pass an explicit snapshot for locked UIKit screens or custom abstractions that must keep the same variant until the app deliberately redraws or reloads that view.

resolveOptimizedEntry does not fetch Contentful entries, evaluate audiences, call the Experience API, or mutate state. SwiftUI OptimizedEntry wraps the same boundary and adds component-level behavior such as variant locking, live updates, and interaction tracking.

For the full data model and fallback behavior, see Entry optimization and variant resolution.

Tracking mechanics

The iOS SDK emits mobile screen events, custom business events, and Contentful entry interaction events:

SDK-managed entry interaction tracking uses these defaults:

• Entry view and tap tracking are enabled by default.
• Initial view event after 2 seconds at 80% visibility.
• Periodic duration updates every 5 seconds while the entry remains visible.
• Final duration update when the entry leaves view after a view event has already fired.
• On iOS/UIKit, backgrounding pauses active view cycles. If the cycle has already emitted a view event, pause() emits a final duration update; foreground resume re-evaluates visibility and starts a fresh cycle when the entry is still eligible.

SwiftUI OptimizedEntry and UIKit ViewTrackingController can tune minVisibleRatio, dwellTimeMs, and viewDurationUpdateIntervalMs per entry. Wrap scrollable SwiftUI content in OptimizationScrollView when view timing needs an accurate viewport.

UIKit does not have automatic component visibility tracking. UIKit apps compute visibility and duration through their own table, collection, or view-controller callbacks. Use ViewTrackingController to apply the SDK visibility timing model, or call client.trackView(TrackViewPayload(...)) directly when an app-owned abstraction already computes view duration. Call client.trackClick(TrackClickPayload(...)) from UIKit control actions or gesture recognizers.

Live updates and preview behavior

SwiftUI OptimizedEntry locks to the first resolved variant by default. Locking prevents content from changing while a visitor is reading it. Enable live updates when a component needs to react to profile changes or preview overrides without a reload.

SwiftUI live-update precedence is:

Opening the preview panel sets client.isPreviewPanelOpen. SwiftUI OptimizedEntry treats that state as a live-update override, so audience and variant overrides apply immediately in those components. When the panel closes, entries that return to locked mode snapshot the current client.selectedOptimizations value and keep the previewed variant. Entries whose global default or per-entry override remains live continue to follow client.selectedOptimizations.

UIKit apps choose their own live-update policy. Subscribe to client.$selectedOptimizations, client.$isPreviewPanelOpen, or client.$previewState and redraw views for live behavior, or keep a selected-optimizations snapshot for locked behavior. Treat client.isPreviewPanelOpen as a reason to redraw in live mode while previewing; the SDK does not automatically rebuild UIKit views.

Offline and app lifecycle delivery

The SDK monitors network reachability. On iOS/UIKit, it also observes app lifecycle events. No configuration is required for the default offline path, and queueing and flushing use the same event-delivery model for SwiftUI and UIKit integrations.

Default delivery behavior:

• Experience events queue in memory when the device is offline.
• Core caps the offline Experience queue at 100 events by default. When the queue is full, it drops the oldest offline events before accepting the next event.
• Insights events batch in memory by profile and flush periodically or when the batch reaches the Core batch threshold.
• Queued events flush when connectivity returns. On iOS/UIKit, the SDK also performs an online best-effort flush when the app moves toward the background; if the device remains offline, queued events wait for reconnect.
• Queues do not survive process death. Keep one OptimizationClient alive for the app or scene lifetime to preserve queued events across transient connectivity changes.

Use OptimizationConfig(queuePolicy:) when production behavior needs non-default delivery constraints. QueuePolicy.offlineMaxEvents changes the Experience offline cap, QueueFlushPolicy configures retry timing, backoff, jitter, failure thresholds, and circuit-open timing, and queue callbacks report offline drops, flush failures, circuit-open events, and recovery. Call client.flush() only for deliberate app-owned checkpoints; reconnect flushing and iOS/UIKit background flushing already perform best-effort delivery.

Related documentation

• Optimization iOS SDK README - Package installation, quick start, and published package status.
• Consent management in the Optimization SDK Suite - Cross-SDK consent, persistence consent, allow-list, and withdrawal policy guidance.
• Locale handling in the Optimization SDK Suite - How SDK Experience/event locales relate to Contentful entry locales.
• Entry optimization and variant resolution - Contentful entry contract, variant fallback behavior, and local resolution mechanics.
• Core state management - Shared state, consent, persistence, event queues, and observable mechanics used through the native bridge.
• Integrate the Optimization iOS SDK in a SwiftUI app - SwiftUI setup flow for OptimizationRoot, OptimizedEntry, screen tracking, and preview panel mounting.
• Integrate the Optimization iOS SDK in a UIKit app - UIKit setup flow for direct OptimizationClient usage, manual entry resolution, tracking, and preview panel mounting.
• iOS reference implementation - Native iOS validation app with SwiftUI and UIKit shells.