NSDictionary to JSON

NSDictionary *dict = [NSDictionary new]; // source
NSData *json_data = [NSJSONSerialization dataWithJSONObject:dict options:NSJSONWritingPrettyPrinted error:nil];
NSString *json = [[NSString alloc] initWithData:json_data encoding:NSUTF8StringEncoding];
NSLog(@"%@", json);