Merge pull request #151 from bizz84/feature/logging-complete-transactions-usage

Additional logging to clarify intended usage of `completeTransactions()`

SwiftyStoreKit/CompleteTransactionsController.swift

@@ -42,6 +42,7 @@ class CompleteTransactionsController: TransactionController {
     func processTransactions(_ transactions: [SKPaymentTransaction], on paymentQueue: PaymentQueue) -> [SKPaymentTransaction] {
 
         guard let completeTransactions = completeTransactions else {
+            print("SwiftyStoreKit.completeTransactions() should be called once when the app launches.")
             return transactions
         }
 

SwiftyStoreKit/PaymentQueueController.swift

@@ -125,6 +125,11 @@ class PaymentQueueController: NSObject, SKPaymentTransactionObserver {
     }
 
     func completeTransactions(_ completeTransactions: CompleteTransactions) {
+        
+        guard completeTransactionsController.completeTransactions == nil else {
+            print("SwiftyStoreKit.completeTransactions() should only be called once when the app launches. Ignoring this call")
+            return
+        }
 
         completeTransactionsController.completeTransactions = completeTransactions
     }