Question

How can I iterate through [NSData bytes] one by one and append them to an NSMutableString or print them using NSLog()?

Answer 1

Rather than appending bytes to a mutable string, create a string using the data:

// Be sure to use the right encoding:
NSString *result = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];

If you really want to loop through the bytes:

NSMutableString *result = [NSMutableString string];
const char *bytes = [myData bytes];
for (int i = 0; i < [myData length]; i++)
{
    [result appendFormat:@"%02hhx", (unsigned char)bytes[i]];
}