Foundation objects (dictionaries, arrays, etc.) are converted to json strings

1. NSDictionary *song = [NSDictionary dictionaryWithObjectsAndKeys:@"i can fly",@"title",@"4012",@"length",@"Tom",@"Singer", nil];  
2.     if ([NSJSONSerialization isValidJSONObject:song])  
3.     {  
4.         NSError *error;  
5. ///Write JSON data as NSData data
6.         NSData *jsonData = [NSJSONSerialization dataWithJSONObject:song options:NSJSONWritingPrettyPrinted error:&error];  
7.         NSString *json =[[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];  
8.         NSLog(@"json data:%@",json);  
9.     }