CODEWITHSUNDEEP
node.jsfirebasefirebase-realtime-databasepromiseonload
now_world
now_world

Reputation: 1096

Firebase waiting to load database data before promise fires

Can someone please explain how to use promises with Firebase with my code below: 

        var p = new Promise(function(resolve, reject) {
            var data=null;

            var ref = db.ref("/");
            ref.once("value", function(snapshot) {
                data = snapshot.val();

            });

            data.onload = function() {
                console.log(data+" onload");

                if (data!=null) {
                    resolve('Success!');
                }
                else {
                    reject('Failure!');
                    console.log('failed');
                }

            }

        });

        p.then(function() { 
            /* do something with the result */
            console.log(data+" done");
        }).catch(function() {
            /* error :( */
            console.log("error");
        });

I'm wanting to wait until I 'hear back' from data = snapshot.val(); before I call my next function. What is the correct way to go about this? I'm clearly not understanding promises. I'm trying to follow this tutorial.

Upvotes: 1

Views: 1837

Answers (1)

deezy
deezy

Reputation: 505

Promises are built into firebase directly.

var ref = firebase.database().ref();

ref.once('value')
  .then(function (result) {
    // This only happens after the data has been returned
    console.log(result.val());
  })
  .catch(function (err) {
    // This is where errors land
    console.log('Error', err.code);
  });

Version 3 of firebase has you covered so you do not need to create container promises. :)

Upvotes: 2

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