NSURL *url = [[NSURL alloc] initFileURLWithPath:@"http://www.w3schools.com/xml/note.xml"];
NSData *xmlData = [[NSData alloc] initWithContentsOfURL:url];

NSError *parseError = nil;
NSDictionary *xmlDictionary = [XMLReader dictionaryForXMLData:xmlData error:&parseError];


NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:xmlDictionary
                                                   options:NSJSONWritingPrettyPrinted
                                                     error:&error];
 NSLog(@"%@", jsonData);

[NSJSONSerialization dataWithJSONObject:options:error:]: value parameter is nil'