iOS IAP, how to judge multiple user at the same device

Question

For example: There are two different game characters in a single iPhone device, we call it A and B.

First, app user login as A, he perform an IAP action, the A logout without the purchase completed.

Then, app user login as B, then purchase finish event arrival, this is the problem, how to judge the receipt belongs to A, not B.

I googled, found SKMutablePayment.requestData may be used for solve this problem, but Apple Document told me this is a reserved property, and must be nil, or else then payment will be reject.

requestData Reserved for future use. (read-only)

@property(nonatomic, copy, readonly) NSData *requestData Discussion The default value is nil. If requestData is not nil, your payment request will be rejected.

Availability Available in iOS 3.0 and later. Declared In SKPayment.h

Answer 1

thanks for everyone's reply

finally, I found SKMutablePayment.applicationUsername can save my private account username, but It only available on iOS7.0.

save:

SKMutablePayment* payment = [SKMutablePayment paymentWithProduct:product];
payment.applicationUsername = @"my_username_1001";

read:

-(void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions
{            
     for (SKPaymentTransaction* trans in transactions) {
        switch (trans.transactionState) {
            case SKPaymentTransactionStateFailed:
                [[SKPaymentQueue defaultQueue] finishTransaction:trans];
                break;
            case SKPaymentTransactionStatePurchased:
                // got private user account here
                NSString* applicationUsername = [[trans payment] applicationUsername];
                break;
            case SKPaymentTransactionStatePurchasing:
                break;
            case SKPaymentTransactionStateRestored:
                break;
        }
    }
}