我在理解链接器命令错误时遇到了问题。我收到以下信息:duplicatesymbol_OBJC_IVAR_$_XYZAddToDoItemViewController._toDoItemin:/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZToDoListViewControll