StoreKit

StoreKit 2 patterns for implementing in-app purchases with async/await APIs, automatic verification, and SwiftUI integration.

Quick Reference

Core Workflow

1. Create .storekit configuration file first (before any code)
2. Test purchases locally in Xcode simulator
3. Implement centralized StoreManager with @MainActor
4. Set up Transaction.updates listener at app launch
5. Display products with ProductView or custom UI
6. Always call transaction.finish() after granting entitlements

Essential Architecture

@MainActor
final class StoreManager: ObservableObject {
    @Published private(set) var products: [Product] = []
    @Published private(set) var purchasedProductIDs: Set<String> = []
    private var transactionListener: Task<Void, Never>?

    init() {
        transactionListener = listenForTransactions()
        Task { await loadProducts() }
    }
}

Common Mistakes

1. Missing .finish() calls on transactions — Forgetting to call transaction.finish() after granting entitlements causes transactions to never complete. The user won't see their purchase reflected. Always call finish().

2. Unsafe StoreManager state — Shared StoreManager without @MainActor can have race conditions. Multiple async tasks can update @Published properties concurrently, corrupting state. Use @MainActor for thread safety.

3. No transaction listener at app launch — Not setting up Transaction.updates listener means app crashes or misses refunded/canceled purchases. Listen for transactions immediately in @main, not when user taps purchase button.

4. Hardcoded product IDs — Hardcoded IDs make testing and localization hard. Use configuration files or environment variables for product IDs. Same applies to prices (fetch from App Store, don't hardcode).

5. Ignoring verification failures — App Store verification fails silently sometimes. Not checking verification status means accepting unverified transactions (security risk). Always verify before granting entitlements.