I have used this method,
NSDictionary *jsonObject=[NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableLea
Just in case anyone is here to see swift code:
NSData to NSDictionary
let dictionary:NSDictionary = NSKeyedUnarchiver.unarchiveObjectWithData(jsonData)! as NSDictionary
NSData to NSString
let resstr = NSString(data: res, encoding: NSUTF8StringEncoding)