我有个奇怪的错误。首先让我解释一下我的数据库结构。我在数据库中存储不同酒店的可预订床位。结构如下:

/beds
|
|- hotel1
|    |---- bed1
|    |
|    |---- bed2
|
|- hotel2
|    |---- bed1
|    |
|    |---- bed2
|
|- hotel3
     etc...

用户可以预先预订一张床,这样当他考虑是否预订时,就没有人可以预订了。有一个5分钟的计时器。为了避免计时器太多,我在服务器中有一个列表,其中包含每个酒店的列表,而每个酒店的每个床位都有一个对象:

const hotelBedTimeouts = [];
var beds = db.ref('/beds');

// Initialise the bed timeout holder object
beds.once("value", function(snapshot){
  var hotels = snapshot.val();

  for (var i = 0; i < hotels.length; i++) {
    // push empty list to be filled with lists holding individual bed timeouts
    if(hotels[i]){
      hotelBedTimeouts.push([]);
      for(var j = 0; j < hotels[i].length; j++) {
        // this list will hold all timeouts for this bed
        hotelBedTimeouts[i].push({});
      }
    } else {
      hotelBedTimeouts.push(undefined);
    }
  }
});

这就是我如何创建空计时器保持器结构的方法。然后,每当客户使用firebase功能预订床位时,我都会设置计时器。当用户退出页面时,我也使用这个函数来取消计时器。

// Frees a bed after a set amount of time
exports.scheduleFreeBed = functions.database.ref('/beds/{hotelIndex}/{bedIndex}/email').onUpdate( (snapshot, context) => {
  var originalEmail = snapshot.after.val();
  var hotelIndex = context.params.hotelIndex;
  var bedIndex = context.params.bedIndex;
  if (originalEmail === -1) {

    console.log("Cancelling timeout for chair number " + bedIndex + " with...");
    console.log("hotelIndex: " + hotelIndex);
    console.log("hotelBedTimeouts[hotelIndex]:");
    console.log(hotelBedTimeouts[hotelIndex]);
    console.log("hotelBedTimeouts[hotelIndex][bedIndex]");
    console.log(hotelBedTimeouts[hotelIndex][bedIndex]);

    clearTimeout(hotelBedTimeouts[hotelIndex][bedIndex].timeoutFunc); // clear current timeoutfunc
    return 0; // Do nothing
  }

  console.log("Setting timeout for bed number " + bedIndex + " with...");
  console.log("hotelIndex: " + hotelIndex);
  console.log("hotelBedTimeouts[hotelIndex]:");
  console.log(hotelBedTimeouts[hotelIndex]);
  console.log("hotelBedTimeouts[hotelIndex][bedIndex]");
  console.log(hotelBedTimeouts[hotelIndex][bedIndex]);

  // replace old timeout function
  hotelBedTimeouts[hotelIndex][bedIndex].timeoutFunc = setTimeout(function () {
    var bedRef = admin.database().ref(`/beds/${hotelIndex}/${bedIndex}`);
    bedRef.once("value", function(bedSnap){
      var bed = bedSnap.val();
      var booked = bed.booked;
      if (!booked) {
        var currentEmail = bed.email;
        // Check if current bed/email is the same as originalEmail
        if (currentEmail === originalEmail) {
          bedSnap.child("email").ref.set(-1, function() {
            console.log("Freed bed");
          });
        }
      }
    });
  }, 300000); // 5 min timeout

  return 0;
});

这在大多数情况下都很有效。但是,如果我同时预定了许多床,那么一些椅子可能会出错。下面是错误的外观:

Cancelling timeout for bed number 24 with...    

hotelIndex: 1

hotelBedTimeouts[hotelIndex]:

undefined

hotelBedTimeouts[hotelIndex][bedIndex]

TypeError: Cannot read property '24' of undefined
    at exports.scheduleFreeBed.functions.database.ref.onUpdate (/user_code/index.js:698:50)
    at Object.<anonymous> (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:112:27)
    at next (native)
    at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:28:71
    at __awaiter (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:24:12)
    at cloudFunction (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:82:36)
    at /var/tmp/worker/worker.js:728:24
    at process._tickDomainCallback (internal/process/next_tick.js:135:7)

看起来像 hotelBedTimeouts[24] 未定义。这让我难以理解,原因有二:

1. 我已经住过了 hotelBedTimeouts 每一家酒店都有一张清单,上面有1-30张床的空物件。 热键超时[24] 因此,不可能对未定义进行评估。
2. 同一张床可以单独预定和取消预定 就在错误之后 .

这个错误的原因是什么?我该如何修复它?