CODEWITHSUNDEEP
javascriptfirebasefirebase-realtime-databasegoogle-cloud-functions
Kermit
Kermit

Reputation: 3417

Firebase database trigger - how to wait for calls

I am having trouble making asynchronous operations in firebase database functions.

I have tried the code below

exports.onTodoCreate = functions
.region('europe-west1')
.database
.ref('/todos/{userId}/{todoId}')
.onCreate( async (snapshot, context) => {
  console.log('Begin')
  //Collect email address
  const email = '[email protected]'

  let otherUser = {}
  let otherUserExists = false
  await snapshot.ref.root.child('users')
  .orderByChild('email')
  .equalTo(email)
  .on('value', (userSnapshot) => {
    userSnapshot.forEach((data) => {
      //Collect data
      otherUser = {
        ...data.val()
      }
      otherUser .id = data.key
      otherUserExists = true
      console.log('otherUserExists-1', otherUserExists)
    })
  })
  console.log('otherUserExists-2', otherUserExists)

The expected output is:

Begin
otherUserExists-1 true
otherUserExists-2 true

What I see in the logs is:

Begin
otherUserExists-2 false
otherUserExists-1 true

How can I make Google Cloud Functions (Firebase database trigger) to wait for the database call to finish before proceeding? I have several calls that needs to be executed asynchronously and wish not to have to nest them to force asynchronous operation.

Upvotes: 1

Views: 733

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317828

on() attaches a persistent listener to a query that will get invoked with the data at that location, and again for each change to any data at that location. The method does not return a promise. This is almost certainly never what you want to do in Cloud Functions.

Instead, if you need to get data a single time, use once(), which returns a promise that resolves with a snapshot of the requested data.

Upvotes: 3

Related Questions