Trying to get ng-csv to work with Firebase - angularjs

Question

I have data stored on Firebase. I have a function that will grab the information from Firebase and return it as an array. I want to be able to use ng-csv to download that file as a .csv however when I download it is an empty file.
Is it possible to use ng-csv if I am trying to grab data from Firebase and if so does anyone have any examples?
Update (from OPs duplicate question):
I am trying to use ng-csv to allow a user to download a .csv file by clicking a button. The information is stored in Firebase and I have created a function that returns the needed information from Firebase as an array. However, I think the problem is when the button is clicked the file is downloaded before the information is pulled from Firebase and loaded, so the .csv file is always empty. Is there a way around this? Here is my code in my main.js app:
this.export = function() {
var results = fireFactory.getResults() //code that returns the array of objects
results.$loaded().then(function(array) {
var test= [];
test.push(array[0]);
test.push(array[1]);
return test;
};
};
Here is my code in my HTML file:
<button class ="btn" ng-csv="main.export()" filename="test.csv">Export</button>
Is there anyway to delay the file downloading until the information has been loaded and returned from the main.export() function?

Answer 1

You are almost there. Frank van Puffelen was on the right path, but stopped short of providing the fix for your code.
return test;
the above statement inside your callback is returning the result inside a promise. This results can only be consumed using promise aware code. Fortunately, ng-csv accepts a promise. If the promise is returned it should work:
this.export = function() {
var results = fireFactory.getResults()
//Here we return the promise for consumption by ng-csv
return results.$loaded().then(function(array) {
var test= [];
test.push(array[0]);
test.push(array[1]);
//the array is returned from the callback, not export
return test;
};
};

Answer 2

You're being tricked by the asynchronous nature in which Firebase loads data. You seem to be thinking that return test; in your original code returns a value from the export function. But if you look more carefully you'll notice that you're actually returning from the (anonymous) callback function.
It's a bit easier to see this, if we separate the callback function out and add some logging statements:
function onDataLoaded(array) {
console.log('Got results from Firebase');
var test= [];
test.push(array[0]);
test.push(array[1]);
return test;
};
this.export = function() {
console.log('Starting to get results from Firebase');
var results = fireFactory.getResults() //code that returns the array of objects
console.log('Started to get results from Firebase');
results.$loaded().then(onDataLoaded);
console.log('Registered result handler');
};
When you call fireFactory.getResults() Firebase will start downloading the data from its servers. Since this may take some time, the downloading happens asynchronously and the browser continues executing your export function, which registers a callback that you want invoked when the data from Firebase is available.
So you'll see the following output in the JavaScript console:
Starting to get results from Firebase
Started to get results from Firebase
Registered result handler
Got results from Firebase