iOS In App Purchase requests login twice

Question

I'm adding In App Purchases to one of my apps. As required, I've added a button to let users re-download purchased items. Here is the IBAction method for that:

- (IBAction)touchedButtonUnlockAgain:(id)sender {
    [self.activityIndicator startAnimating];            
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    [[SKPaymentQueue defaultQueue] restoreCompletedTransactions];

}

When I tap this button, I get the standard login box. I enter my Sandbox username and password (correctly, verified). After that login box disappears, it reappears half a second later. So, I login again with the same username and password (correctly, verified) and THEN the purchases get re-downloaded. I have verified it happens in the Simulator and on a device (iOS 6.0 in both cases).

Why am I getting prompted for my username/password twice?

Answer 1

The only reason for this will be unfinished transactions - the ghosts that wait for their finishTransaction call for redemption. They may exist due to signed-out user initiated transactions that couldn't be finished - or simply due to abrupt app termination before they could finish. Basically, unbalanced calls to addPayment / restoreCompletedTransactions and finishTransaction can cause them.

Check your delegates: paymentQueue:RestoreCompletedTransactionsFinished: & paymentQueue:restoreCompletedTransactionsFailedWithError:

Are you doing anything twice? Do you receive any error?

One more thing to check is: When in your app life cycle do you call following statement?

[[SKPaymentQueue defaultQueue] addTransactionObserver]

This is important to be called as early as possible - because sometimes lost transactions that turn ghosts due to app termination appear again - expecting to be finished. Without an active observer, they don't hit updatedTransactions method which is their final gateway to finishTransaction call.