How to do in-app purchase in ios5?

- (void)viewDidLoad {
if ([SKPaymentQueue canMakePayments]) {
NSLog(@"Can Buy Product");

SKProductsRequest *productRequest=[[SKProductsRequest alloc]initWithProductIdentifiers:[NSSet setWithObject:@"com.mycompany.myproduct.productpack"]];
productRequest.delegate=self;
[productRequest start];
}
else {

NSLog(@"Product Can't be purchased");
}
}

-(IBAction)purchasePack1 {

SKPayment *payment=[SKPayment paymentWithProductIdentifier:@"com.mycompany.myproduct.productpack"];
[[SKPaymentQueue defaultQueue] addTransactionObserver:self];
[[SKPaymentQueue defaultQueue] addPayment:payment];

}

-(void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response {

validProduct=nil;
int count=[response.products count];
if (count>0) {
NSLog(@"Product Avail");

validProduct=[response.products objectAtIndex:0];
}
else {
NSLog(@"No Product avail");
[purchaseBtn setHidden:TRUE];
}
}

-(void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions {

for (SKPaymentTransaction *transaction in transactions) {
switch (transaction.transactionState) {
case SKPaymentTransactionStatePurchasing:
NSLog(@"Purchasing");
[activityIndicatorObj setHidden:FALSE];
[activityIndicatorObj startAnimating];
break;

case SKPaymentTransactionStatePurchased:

UIAlertView *alt=[[UIAlertView alloc]initWithTitle:@"Congrats" message:@"Thanks For Purchasing " delegate:self cancelButtonTitle:@"Dismiss" otherButtonTitles:nil];
[alt show];
[alt release];
NSLog(@"Purchased");
[activityIndicatorObj stopAnimating];
[activityIndicatorObj setHidden:TRUE];
[[SKPaymentQueue defaultQueue] finishTransaction:transaction];
break;

case SKPaymentTransactionStateFailed:

if (transaction.error.code!=SKErrorPaymentCancelled) {

NSLog(@"Cancelled");

}
[[SKPaymentQueue defaultQueue] finishTransaction:transaction];

UIAlertView *alt1=[[UIAlertView alloc]initWithTitle:@"Sorry" message:@"Some Error Encountered!" delegate:self cancelButtonTitle:@"Dismiss" otherButtonTitles:nil];
[alt1 show];
[alt1 release];
NSLog(@"Failed");
[activityIndicatorObj stopAnimating];
[activityIndicatorObj setHidden:TRUE];
break;

case SKPaymentTransactionStateRestored:
NSLog(@"Restored");
[activityIndicatorObj stopAnimating];
[activityIndicatorObj setHidden:TRUE];
[[SKPaymentQueue defaultQueue] finishTransaction:transaction];
break;

default:
break;
}
}
}