Laravel模型中的空数字属性在递减时是否会变为负值？

Question

我正在尝试学习本教程在function createReservation()函数中：

while (strtotime($date) < strtotime($end_dt)) 
{
    $room_calendar = RoomCalendar::where('day','=',$date)
        ->where('room_type_id','=',$room_info['id'])->first();

    $night =  ReservationNight::create();
    $night->day=$date;

    $night->rate=$room_calendar->rate;
    $night->room_type_id=$room_info['id'];
    $night->reservation_id=$reservation->id;

    $room_calendar->availability--;
    $room_calendar->reservations++;

    $room_calendar->save();
    $night->save();

    $date = date ("Y-m-d", strtotime("+1 day", strtotime($date)));
}

$room_calendar->availability没有默认值。那么当它减少时它不会变成负面的吗？

Answer 1

如果可用性的数据库列是无符号整数，它将变为负数，并且还会抛出错误。

您可以在查询中解决您的问题。当你查询$room_calendar时，在你的while循环中

$room_calendar = RoomCalendar::where('day','=',$date)
                 ->where('room_type_id','=',$room_info['id'])
                 ->where('availability','>=',0) 
                 ->first();

之后还在代码中放置一个if块来检查$ room_calendar是否大于零。

像这样的东西

if($room_calendar->count())
{
   $night =  ReservationNight::create();
   $night->day=$date;

   $night->rate=$room_calendar->rate;
   $night->room_type_id=$room_info['id'];
   $night->reservation_id=$reservation->id;

   $room_calendar->availability--;
   $room_calendar->reservations++;

   $room_calendar->save();
   $night->save();

   $date = date ("Y-m-d", strtotime("+1 day", strtotime($date)));
}

通过这种方式，您将无法获得任何零空间。

希望这会有所帮助。