Verifying a Receipt with the App Store - iphone

Question

Retrieve the receipt data from the transaction’s transactionReceipt property and encode it using base64 encoding.
How can I encode NSData using base64 encoding? Please give the code for that.
EDIT
I did it. but now the response is
{exception = "java.lang.NullPointerException"; status = 21002;}
my recipt verification method is this
-(BOOL)verifyReceipt:(SKPaymentTransaction *)transaction
{
NSString *recieptString = [transaction.transactionReceipt base64EncodingWithLineLength:0];
NSLog(#"%#",recieptString);
ASIFormDataRequest *request = [[ASIFormDataRequest alloc] initWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"https://buy.itunes.apple.com/verifyReceipt"]]];
[request setPostValue:recieptString forKey:#"receipt-data"];
[request setPostValue:#"95140bdac98d47a2b15e8e5555f55d41" forKey:#"password"];
[request start];
NSDictionary* subsInfo = [[request responseString] JSONValue];
NSLog(#"%#",subsInfo);
return subscriptionEnabled;
}
Where
NSString *recieptString = [transaction.transactionReceipt base64EncodingWithLineLength:0];
returns me base64 encoded string.
I also tried
NSString *recieptString = [transaction.transactionReceipt base64EncodingWithLineLength:[transaction.transactionReceipt length]];
but response is same.
can any one of you let me know where I could be wrong.
Thanks-

Answer 1

+ (NSString*)base64forData:(NSData*)theData {
const uint8_t* input = (const uint8_t*)[theData bytes];
NSInteger length = [theData length];
static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
NSMutableData* data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
uint8_t* output = (uint8_t*)data.mutableBytes;
NSInteger i;
for (i=0; i < length; i += 3) {
NSInteger value = 0;
NSInteger j;
for (j = i; j < (i + 3); j++) {
value <<= 8;
if (j < length) {
value |= (0xFF & input[j]);
}
}
NSInteger theIndex = (i / 3) * 4;
output[theIndex + 0] = table[(value >> 18) & 0x3F];
output[theIndex + 1] = table[(value >> 12) & 0x3F];
output[theIndex + 2] = (i + 1) < length ? table[(value >> 6) & 0x3F] : '=';
output[theIndex + 3] = (i + 2) < length ? table[(value >> 0) & 0x3F] : '=';
}
return [[[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding] autorelease];
}

Answer 2

You need to post your receipt to "https://sandbox.itunes.apple.com/verifyReceipt" while testing in the sandbox environment.