Firebase Functions error: .once is not a function

问题

I am trying to deploy a simple function to Firebase, but I am having some difficulties. Every time I try to use .once on a reference Firebase tells me that it is not a function. Here is my code

exports.testFunction = functions.database.ref('/Rooms/{firstID}/{pushId}/On').onWrite(event => {
  const value = event.data.val();
  var ref = functions.database.ref(roomNum);
  return ref.once('value').then(snapshot => {
    console.log(snapshot.numChildren);
    return true;
  }); });

I have also tried the following:

firebaseRef.once('value', function(dataSnapshot) {
  console.log(snapshot.numChildren);
});

Nothing seems to work. Does anyone know of a fix or a different way of getting the number of children from a ref/snapshot?

Thank you.

回答1:

functions.database.ref is a different object than the one you're used to using on the client. It's sole purpose is to listen for writes using it's only function, onWrite.

You can obtain your intended ref thru the event parameter.

var ref = event.data.ref

This is a reference to the path you specified in onWrite.

If you want the root reference:

var rootRef = event.data.ref.root

Further reading: https://firebase.google.com/docs/reference/functions/functions.database

来源：https://stackoverflow.com/questions/44574157/firebase-functions-error-once-is-not-a-function

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javascript