storekit

# StoreKit 2 In-App Purchases and Subscriptions

Implement in-app purchases, subscriptions, paywalls, and StoreKit testing using
StoreKit 2. Use the modern Swift-based `Product`, `Transaction`,
`PurchaseAction`, `StoreView`, and `SubscriptionStoreView` APIs. Avoid original
In-App Purchase APIs (`SKProduct`, `SKPaymentQueue`) unless legacy OS support
requires them.

StoreKit views initiate purchases automatically. For custom controls, use
`PurchaseAction` in SwiftUI, `purchase(confirmIn:options:)` in UIKit/AppKit, and
`product.purchase(options:)` on watchOS.

## Contents

- [Product Types](#product-types)
- [Loading Products](#loading-products)
- [Purchase Flow](#purchase-flow)
- [Transaction.updates Listener](#transactionupdates-listener)
- [Entitlement Checking](#entitlement-checking)
- [SubscriptionStoreView (iOS 17+)](#subscriptionstoreview-ios-17)
- [StoreView (iOS 17+)](#storeview-ios-17)
- [Subscription Status Checking](#subscription-status-checking)
- [Restore Purchases](#restore-purchases)
- [App Transaction (App Purchase Verification)](#app-transaction-app-purchase-verification)
- [Purchase Options](#purchase-options)
- [SwiftUI Purchase Callbacks](#swiftui-purchase-callbacks)
- [Common Mistakes](#common-mistakes)
- [Review Checklist](#review-checklist)
- [References](#references)

## Product Types

| Type | Enum Case | Behavior |
|---|---|---|
| **Consumable** | `.consumable` | Used once, can be repurchased (gems, coins) |
| **Non-consumable** | `.nonConsumable` | Purchased once permanently (premium unlock) |
| **Auto-renewable** | `.autoRenewable` | Recurring billing with automatic renewal |
| **Non-renewing** | `.nonRenewing` | Time-limited access without automatic renewal |

## Loading Products

Define product IDs as constants. Fetch products with `Product.products(for:)`.

```swift
import StoreKit

enum ProductID {
    static let premium = "com.myapp.premium"
    static let gems100 = "com.myapp.gems100"
    static let monthlyPlan = "com.myapp.monthly"
    static let yearlyPlan = "com.myapp.yearly"
    static let all: [String] = [premium, gems100, monthlyPlan, yearlyPlan]
}

let products = try await Product.products(for: ProductID.all)
for product in products {
    print("\(product.displayName): \(product.displayPrice)")
}
```

## Purchase Flow

Prefer StoreKit views for standard paywalls because they initiate purchases,
restore purchases, and display policy controls. For custom SwiftUI purchase
buttons, prefer `PurchaseAction` from the environment. Use direct
`product.purchase(options:)` for watchOS, and use `purchase(confirmIn:options:)`
for UIKit or AppKit confirmation. Always handle every `PurchaseResult`, verify
before access, deliver durably, then finish.

```swift
@Environment(\.purchase) private var purchase

func purchaseProduct(_ product: Product) async throws {
    let result = try await purchase(product, options: [
        .appAccountToken(userAccountToken)
    ])
    switch result {
    case .success(let verification):
        let transaction = try checkVerified(verification)
        await deliverContent(for: transaction)
        await transaction.finish()
    case .userCancelled:
        break
    case .pending:
        // Ask to Buy or deferred approval: show pending UI, no unlock yet.
        showPendingApprovalMessage()
    @unknown default:
        break
    }
}

func checkVerified<T>(_ result: VerificationResult<T>) throws -> T {
    switch result {
    case .verified(let value): return value
    case .unverified(_, let error): throw error
    }
}
```

## Transaction.updates Listener

Start at app launch, not when a paywall appears. Catches purchases from other
devices, Family Sharing changes, renewals, Ask to Buy approvals, refunds,
revocations, and unfinished transactions Apple emits once immediately after
launch. Keep the task retained for the app lifetime.

```swift
@main
struct MyApp: App {
    private let transactionListener: Task<Void, Never>

    init() {
        transactionListener = Self.listenForTransactions()
    }

    var body: some Scene {
        WindowGroup { ContentView() }
    }

    static func listenForTransactions() -> Task<Void, Never> {
        Task(priority: .background) {
            for await result in Transaction.updates {
                guard case .verified(let transaction) = result else { continue }
                await StoreManager.shared.updateEntitlements()
                await transaction.finish()
            }
        }
    }
}
```

## Entitlement Checking

`Transaction.currentEntitlements` emits non-consumables, active or grace-period
auto-renewable subscriptions, and the latest non-renewing subscription
transaction—including finished ones. It excludes consumables and refunded or
revoked products. Track consumable fulfillment separately, and apply the app's
expiration policy to non-renewing subscriptions before granting access.

```swift
@Observable
@MainActor
class StoreManager {
    static let shared = StoreManager()
    var purchasedProductIDs: Set<String> = []
    var isPremium: Bool { purchasedProductIDs.contains(ProductID.premium) }

    func updateEntitlements() async {
        var purchased = Set<String>()
        for await result in Transaction.currentEntitlements {
            if case .verified(let transaction) = result,
               transaction.revocationDate == nil {
                if transaction.productType == .nonRenewing,
                   transaction.expirationDate.map({ $0 <= .now }) ?? true {
                    continue
                }
                purchased.insert(transaction.productID)
            }
        }
        purchasedProductIDs = purchased
    }
}
```

### SwiftUI .currentEntitlementTask Modifier

```swift
struct PremiumGatedView: View {
    @State private var state: EntitlementTaskState<VerificationResult<Transaction>?> = .loading

    var body: some View {
        Group {
            switch state {
            case .loading: ProgressView()
            case .failure: PaywallVie