Sending firebase database data to client through cloud function

Question

I am trying to send data from my firebase database back to my client in a cloud function. I want to return the entire json child object. Here is the code for my cloud function:

exports.addNumbers = functions.https.onCall((data, context) => {
 admin.database().ref('store/ingredients').once('value', function(snapshot) {
    
    return snapshot.val();

  });

});

Here is my client code that is invoking this cloud function and accessing its data:

const addNumbers = firebase.functions().httpsCallable('addNumbers');
  addNumbers().then(result => {
    console.log(result.data + "in client");
  });

But the data returned in the client is null and the cloud function is returning only object [Object] in the firebase logs. Please someone help me.

Frank van Puffelen Frank van Puffelen · Accepted Answer · 2021-01-17T02:28:25

You're almost there. You just need to return something from the top-level code in your Cloud Function.

The easiest way is to use a then clause:

exports.addNumbers = functions.https.onCall((data, context) => {
  return admin.database().ref('store/ingredients').once('value').then((snapshot) => {
    return snapshot.val();
  });
});

Now the value from the database "bubbles up" to the calling code, and is then returned out of your function as a promise.

On modern JavaScript versions, you can make this code easier to read by using async/await:

exports.addNumbers = functions.https.onCall(async (data, context) => {
  let snapshot = await admin.database().ref('store/ingredients').once('value')
  return snapshot.val();
});

This works exactly the same under the hood (it's really just syntactic sugar), but most developers find it much easier to read.

Sending firebase database data to client through cloud function

1 Answers