类描述符

类描述符应该使用 andfunctions 读取和编写，如下所示：readAddress()writeAddress()

AcDbDwgFiler *pFiler = NULL;
if ((pFiler = undoFiler()) != NULL) {
undoFiler()->writeItem((long)AsdkPoly::desc()); // Wrong!
...
undoFiler()->writeAddress(AsdkPoly::desc()); // Right
...

}