DispatchGroup issue when authenticate apple Id

问题

I have one weird issue right now. I am using DispatchGroup() to verify in-app subscriptions on load. It works only if I have already authenticated with apple id.

    let dispatchGroup = DispatchGroup()

    var index = 0  // <--- Just For test
    for a in inAppPurchaseIds {
        index = index + 1
        print("INDEX ENTER --> \(index)")
        dispatchGroup.enter()   // <<---

        MPInAppPurchases.verifySubscription(a) { [weak self] status, data, error, expDate in
            print("LOOP COUNT --> YES")

            guard let me  = self else {
                print("INDEX LEAVE ME --> \(a)")

                dispatchGroup.leave()
                return
            }

            print("DATA ---- \(String(describing: data))")

            print("INDEX LEAVE --> \(a)")

            dispatchGroup.leave()
        }
    }

    dispatchGroup.notify(queue: .main) {
        print("NOTIFY")
    }

Function that verifies receipt

 static func verifySubscription(_ id: String, completion: purchaseHandler?) {
    let appleValidator = AppleReceiptValidator(service: .production, sharedSecret: sharedSecret)
    SwiftyStoreKit.verifyReceipt(using: appleValidator) { result in
        switch result {
        case .success(let receipt):
            // Verify the purchase of a Subscription
            let purchaseResult = SwiftyStoreKit.verifySubscription(
                ofType: .autoRenewable, // or .nonRenewing (see below)
                productId: id,
                inReceipt: receipt)

            switch purchaseResult {
            case .purchased(let expiryDate, _):
                print("\(id) is valid until \(expiryDate)")
                completion?(true, "Product Purchased", nil, expiryDate)
            case .expired(let expiryDate, _):
                print("\(id) is expired since \(expiryDate)")
                completion?(false, "Product Expired", nil, expiryDate)
            case .notPurchased:
                print("The user has never purchased \(id)")
                completion?(false, "Product Not Purchased", nil, nil)
            }

        case .error(let error):
            print("Receipt verification failed: \(error)")
            completion?(false, "Receipt verification failed", error.localizedDescription, nil)
        }
    }
}

LOG

INDEX ENTER --> 1
INDEX ENTER --> 2
INDEX ENTER --> 3

LOOP COUNT --> YES
DATA ---- Optional("Product Not Purchased")
INDEX LEAVE --> kr.co.proPackage

The function returns data on completion but here I am unable to get any data from the function and only once it leaves the group. Any idea why this happens? This does happens only when I am not logged in with my apple id in my device. Once its done, it works perfectly.

Steps to reproduce the issue

Log out from my apple id > remove an app from my device > relaunch the app.

来源：https://stackoverflow.com/questions/55294986/dispatchgroup-issue-when-authenticate-apple-id