iOS In-App Purchases restore previous purcases safely - iphone

Question

I have implemented an In-App Purchase in my app and I have two questions about it. This is the code I use:
- (IBAction)buyProduct1:(id)sender {
SKPayment *payment = [SKPayment paymentWithProduct:product1];
[[SKPaymentQueue defaultQueue] addTransactionObserver:self];
[[SKPaymentQueue defaultQueue] addPayment:payment];
}
- (IBAction)restorePurchases:(id)sender {
[[SKPaymentQueue defaultQueue] addTransactionObserver:self];
[[SKPaymentQueue defaultQueue] restoreCompletedTransactions];
}
- (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions {
for (SKPaymentTransaction *transaction in transactions) {
switch (transaction.transactionState) {
case SKPaymentTransactionStatePurchasing:
break;
case SKPaymentTransactionStatePurchased:
//Can I be 100% sure that this method is only called when the product is bought?
[self product1Bought:transaction];
break;
case SKPaymentTransactionStateRestored:
//What code should I have here to safely restore product1 if the product is bought?
break;
case SKPaymentTransactionStateFailed:
break;
default:
break;
}
}
}
- (void)product1Bought:(SKPaymentTransaction *)transaction {
NSString *string = #"Product1";
[[NSUserDefaults standardUserDefaults] setObject:string forKey:#"Product1"];
NSLog(#"Product1 is bought");
[[SKPaymentQueue defaultQueue] finishTransaction:transaction];
}
1.I was just wondering if I can be 100% sure that the productBought method is only called after a successfully purchase and not if anything strange happens and the product wasn't really purchased?
2.How can I check if product1 is purchased earlier so I can call the product1Bought method?

Answer 1

- (void)paymentQueueRestoreCompletedTransactionsFinished:(SKPaymentQueue *)queue
{
if ([queue.transactions count] == 0)
{
UIAlertView *restorealert = [[UIAlertView alloc]
initWithTitle:#"Restore"
message:#"There is no products purchased by you"
delegate:self
cancelButtonTitle:#"Ok"
otherButtonTitles:nil];
[restorealert show];
activityIndicator.hidden = YES;
}
else
{
NSString *productID;
for(SKPaymentTransaction *transaction in queue.transactions)
{
productID = transaction.payment.productIdentifier;
NSLog(#"the product identifier is %#",productID);
}
here after completing your restore you can get the productId which you bought

Answer 2

1) is working fine and the data will be available when user purchases it
2) for the early purchased items you can call this method under SKPaymentTransactionStateRestored:
[self RestorePurchases];
-(void)RestorePurchases{
[[SKPaymentQueue defaultQueue] restoreCompletedTransactions];
}