RestoreCompletedTransactions() 没有调用 paymentQueue UpdatedTransactions？

我在 Swift 4/iOS 11 中恢复 IAP 时遇到问题。我的AppDelegate实施SKPaymentTransactionObserver. In AppDelegate's didFinishLaunchingWithOptions我正在打电话SKPaymentQueue.default().add(self)。我实施paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction])AppDelegate 中也有这个函数。

From a ViewController我可以这样购买：

let payment = SKPayment(product: products.first!)
SKPaymentQueue.default().add(payment)

购买成功完成 - 我收到updatedTransaction与状态.purchased in my paymentQueue观察者。

但是，当我从同一个调用以下内容时ViewController为了恢复购买：

SKPaymentQueue.default().restoreCompletedTransactions()

the paymentQueue updatedTransactions函数永远不会被调用。

看来我的沙箱用户等设置正确，因为初始购买正在运行。沙盒用户有能力恢复购买吗？除了打电话之外我还需要做任何额外的工作吗restoreCompletedTransactions()恢复购买？

更新一下，这是我的paymentQueue updatedTransactions存在于的代码AppDelegate:

func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
    for transaction in transactions{
        switch transaction.transactionState{
        case .purchased:
            debugPrint("purchased it!")
            menuDelegate?.unlockMenu()
            //unlock the content, then
            SKPaymentQueue.default().finishTransaction(transaction)
            break
        case .failed:
            debugPrint("failed")
            SKPaymentQueue.default().finishTransaction(transaction)
            break
        case .restored:
            debugPrint("restored")
            menuDelegate?.unlockMenu()
            //unlock the content, then
            SKPaymentQueue.default().finishTransaction(transaction)
            break
        case .purchasing:
            debugPrint("purchasing...")
            break
        case .deferred:
            debugPrint("deferred...")
            break
        }
    }
}