# Migrating from StoreKit

OnsideKit is modeled on StoreKit's original (`SKPaymentQueue`-based) API, so most concepts map directly. This page lists the equivalents and the differences worth knowing.

## Type mapping

<table><thead><tr><th width="340">StoreKit</th><th>OnsideKit</th></tr></thead><tbody><tr><td><code>SKPaymentQueue.default()</code></td><td><code>Onside.defaultPaymentQueue()</code></td></tr><tr><td><code>SKPayment</code></td><td><code>OnsidePayment</code></td></tr><tr><td><code>SKPaymentTransaction</code></td><td><code>OnsidePaymentTransaction</code></td></tr><tr><td><code>SKPaymentTransactionState</code></td><td><code>OnsidePaymentTransactionState</code></td></tr><tr><td><code>SKPaymentTransactionObserver</code></td><td><code>OnsidePaymentTransactionObserver</code></td></tr><tr><td><code>SKProductsRequest</code></td><td><code>OnsideProductsRequest</code> (via <code>Onside.makeProductsRequest(productIdentifiers:)</code>)</td></tr><tr><td><code>SKProductsRequestDelegate</code></td><td><code>OnsideProductsRequestDelegate</code></td></tr><tr><td><code>SKProduct</code></td><td><code>OnsideProduct</code></td></tr><tr><td><code>SKProductSubscriptionPeriod</code></td><td><code>OnsidePeriod</code></td></tr><tr><td><code>finishTransaction(_:)</code></td><td><code>finishTransaction(_:)</code></td></tr><tr><td><code>restoreCompletedTransactions()</code></td><td><code>restoreCompletedTransactions(completion:)</code></td></tr></tbody></table>

## Key differences

* **Queue accessor.** Use `Onside.defaultPaymentQueue()` — not `SKPaymentQueue.default()`, and not `Onside.paymentQueue()`.
* **Completion arguments are required.** `add(_:completion:)` and `restoreCompletedTransactions(completion:)` take a non-defaulted `completion` (pass a closure or `nil`). The completion reports only the pre-flight outcome (e.g. `.loginDiscarded`); transaction updates still arrive via the observer.
* **Login is built in.** OnsideKit presents login on demand when a purchase/restore needs it — there's no separate StoreKit-style account check. See [Authentication & User Account](/sdk/core-concepts/authentication.md).
* **Product identifiers are Onside slugs.** `OnsideProduct.productIdentifier` is the identifier you configure in the Onside console and request with — not an App Store SKU.
* **`appAccountToken` via mutation.** `OnsidePayment`'s only initializer is `init(product:)`; set `appAccountToken` by mutating the value (`var payment = OnsidePayment(product:); payment.appAccountToken = ...`).
* **Resilient enums.** OnsideKit enums are non-frozen; include `@unknown default` in `switch` statements. See [Threading & Object Lifetime](/sdk/core-concepts/threading-and-retention.md).
* **Storefront safety gate.** When the storefront/price changes for a queued purchase, OnsideKit asks your [`OnsidePaymentQueueDelegate`](/sdk/purchasing/storefront-price-changes.md) before continuing.


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