Using Firebase Push key as Key in Second Push

Question

I'm trying to add two related items to my Firebase database. I want to push one item, then get that item's newly created key and use it as the key for the second item in a different tree. I've tried querying the database to get the last key created and using it as the key for the second push, but it's still just generating a new key for it. Here's the code that I'm using:

save: function() {
    if (this.$.document.isNew && (this.editableCard.title || this.editableCard.body)) {
        return this.$.document.save(this.cardsPath).then(function() {
            this.$.document.reset();
            var sceneRef = firebase.database().ref().child(this.cardsPath);
            var scene = sceneRef.orderByKey().limitToLast(1);
            var sceneKey = scene.key;
            this.$.document.save('/documents/', sceneKey);
        }.bind(this));
    }
    return Promise.resolve();
}

(I'm using Polymer, and my starting point is the note-app demo for Polymerfire).

Any ideas on how I can retrieve the new key of the first push and use it for the second push? Thanks!

EDIT

I found the answer in Firebase's documentation for Reading and Writing to the database for Web. Link

Answer 1

push() returns a DatabaseReference immediately. You can ask that reference what its key is, using getKey() , then use that string to update another location in your database.

Answer 2

You can access the key property on the original database reference and use that as the key for the second one, like so:

let firstObjRef = firebase.database().ref('/first/path/).push(firstObj, (error) => {
  videoObj["roomUploadedTo"] = this.roomName;
  var updateObj = {};
  updateObj[videoObjRef.key] = videoObj;

  firebase.database().ref('/second/path/').update(updateObj).then( (e) => {
    console.log('update went through. booyah! ' + e);
  })