I would like to throw a warning message when users try to add an int to an nsmutablearray basically any insert statement that includes values that are not nsstring / nsnumber cause run time crashes. It's exactly the same crash you get when you type %@ instead of %d NSLog(int); The crash is ok, but I want to throw a friendly 'FATAL' message to user. so far I have this try catch with isKindOfClass NSObject but ints are slipping through. #define FATAL_MSG "FATAL: object is not an NSObject subclass. Are you using int? use [NSNumber numberWithInt:1] \n" #define VAToArray(firstarg) ({\ NSMutableArray* valistArray = [NSMutableArray array];\ id obj = nil;\ va_list arguments;\ va_start(arguments, sql);\ @try { \ while ((obj = va_arg(arguments, id))) {\ if([obj isKindOfClass:[NSObject class]]) [valistArray addObject:obj];\ else printf(FATAL_MSG); \ }\ } \ @catch(NSException *exception){ \ printf(FATAL_MSG); \ } \ va_end(arguments);\ valistArray;\ }) - (void)test:(NSString*)sql,... { NSLog(@"VAToArray :%@",VAToArray(sql)); } // then call this [self test:@"str",@"test",nil]; when I call this [self test:@"str",2,nil]; throw the error message.