ios - getting invalid product id (in-app purchase) -

i'm using method validate products: - array of products, first parse xml file downloaded server, , list of products, ids invalid.

- (void) validateproductsidentifiers:(nsarray *) products {  nsmutablearray *productsids = [[nsmutablearray alloc] init];  if (products != nil) {      (ejbookinstore * book in products) {         //for each book, save book id         [productsids addobject:[book idbook]];     }     //verify if array not empty     if ([productsids count] > 0) {          skproductsrequest *productsrequest = [[skproductsrequest alloc] initwithproductidentifiers:[nsset setwitharray:productsids]];         productsrequest.delegate = self;         [productsrequest start];     } } else {      nslog(@"erro..."); } 

when put id directly in method, id validate:

   - (void) validateproductsidentifiers:(nsarray *) products {      nsmutablearray *productsids = [[nsmutablearray alloc] init];      if (products != nil) {           (ejbookinstore * book in products) {             //for each book, save book id             [productsids addobject:[book idbook]];         }         //verify if array not empty         if ([productsids count] > 0) {             //when set id this, id validated             nsarray *prodids = [nsarray arraywithobjects:@"com.example.booka", nil];             skproductsrequest *productsrequest = [[skproductsrequest alloc] initwithproductidentifiers:[nsset setwitharray: prodids]];             productsrequest.delegate = self;             [productsrequest start];         }     } else {          nslog(@"error...");     } }