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如何在then语句中定义firebase cloud函数触发器

google-cloud-functions firebase javascript

Sahand · 技术社区 · 6 年前

我需要确保在定义firebase函数之前运行此代码,因为它取决于代码中的变量集:

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);
    }
  }
});

有人建议我把这个函数放在 .then() 声明之后 once() 打电话来。所以我试了一下:

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);
    }
  }
}).then( () => {
  // Frees a bed after a set amount of time
  exports.scheduleFreeBed = functions.database.ref('/beds/{hotelIndex}/{bedIndex}/email').onUpdate( (snapshot, context) => {
     // My code
});

不幸的是,这导致我的整个firebase函数被删除:

$ firebase deploy --only functions

=== Deploying to 'company-23uzc'...

i  functions: deleting function scheduleFreeBed...
â  functions[scheduleFreeBed]: Successful delete operation.

可以用这种方式定义一个firebase函数吗?

如何确保firebase函数始终能够访问后端代码中定义的某些变量?

编辑:

这是我在道格·史蒂文森(Doug Stevenson)回答之后第一次尝试解决问题:

const hotelBedTimeouts = [];
var beds = db.ref('/beds');
const promise = beds.once("value");

// Frees a bed after a set amount of time
exports.scheduleFreeBed = functions.database.ref('/beds/{hotelIndex}/{bedIndex}/email').onUpdate( (snapshot, context) => {

  promise.then( (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);
        }
      }
    });

  var originalEmail = snapshot.after.val();
  var hotelIndex = context.params.hotelIndex;
  var bedIndex = context.params.bedIndex;
  if (originalEmail === -1) {
    clearTimeout(hotelBedTimeouts[hotelIndex][bedIndex].timeoutFunc); // clear current timeoutfunc
    return 0; // Do nothing
  }

  // replace old timeout function
  hotelBedTimeouts[hotelIndex][bedIndex].timeoutFunc = setTimeout(function () { // ERROR HERE
    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;
});

不过,在执行函数时,似乎还没有正确定义hotelBedTimeouts,请看下面的错误:

TypeError: Cannot read property '15' of undefined

我在代码中的注释中标记了此错误的目的行。

名单怎么还没有定义?

1 回复 | 直到 6 年前

Doug Stevenson 6 年前

Firebase CLI不支持这种类型的函数定义。相反,你应该开始最初的工作里面函数,然后缓存结果,这样就不必再次执行它了。或者,您可以尝试开始工作,并保留一个承诺,该功能可以在以后使用,例如:

const promise = doSomeInitialWork()  // returns a promise that resolves with the data

exports.scheduleFreeBed = functions.database.ref(...).onUpdate(change => {
    promise.then(results => {
        // work with the results of doSomeInitialWork() here
    })
})