How do I check if a product has already been purchased by the user on iOS?

Question

Guys, when I want to validate if a product of my application (an Inapp) has already been purchased by the user, on Windows Phone I just check the product through Licenceinformation. For example:

var license = CurrentApp.LicenseInformation.ProductLicenses["id_do_meu_produto"];
if (!license.IsActive) 
{
  // O usuário ainda não comprou este item
  ...
}

Now the question: Can you do this on iOS? A friend who has an app posted to the Apple Store says it’s hopeless without first forcing the user to log in to the store.

How to check if the user has already paid for an item?

Unfortunately some users (few) are buying the product and then asking for extortion for Apple. So they get the product for free.

Answer 1

try like this:

- (void) verificaItensComprados {
   [[SKPaymentQueue defaultQueue] restoreCompletedTransactions];
}//chame essa funçao

//no delegate da funcao
- (void) paymentQueueRestoreCompletedTransactionsFinished:(SKPaymentQueue *)queue {
  itensCompradosIDs = [[NSMutableArray alloc] init];

  NSLog(@"numero de produtos a ser restabelecido: %i", queue.transactions.count);
  for (SKPaymentTransaction *transaction in queue.transactions)
  {
      NSString *produtoID = transaction.payment.productIdentifier;
      [itensCompradosIDs addObject:produtoID];
  }
}