AngularFire: How to update a $firebaseArray by extending the service and using the $$updated private method

I have two separate lists of Posts and Authors in my database, each Post containing an authorId to refer to the corresponding author.

The following method helps me retrieve the whole list of Posts by systematically including the name of the author for each Post:

app.factory('NormalizedPosts', function($firebaseArray, FirebaseFactory) {
    var PostsWithAuthors = $firebaseArray.$extend({

        // override $$added to include author name
        $$added: function(snap) {
            var record = $firebaseArray.prototype.$$added.call(this, snap);

            FirebaseFactory.$getAuthorId( record.authorId ).$loaded(function( authorData ) {
                record.authorData = authorData;
            });

            return record;
        },

        // ????????
        $$updated: function(snap) { 

            var rec = $firebaseArray.prototype.$$updated.call(this, snap); 
            var updatedRecord = this.$getRecord(snap.key()); 

            FirebaseFactory.$getAuthorId( updatedRecord.authorId )
            .$loaded(function( authorData ) { 
                rec.authorData = authorData; 
            }); 

        return rec; 

        }

    });

    return PostsWithAuthors;
});

PS: The FirebaseFactory is just a wrapper for firebase methods.

I then call

var list = new NormalizedPosts ( new Firebase(FBURL).child("posts") ); 

in my controller to get the full list. This works great.

I'm scratching my head with what should go into the $$updated method: When a new Post is added, the list gets updated as expected (through the $$added method). But when there's a change in a Post data (e.g. the post title), my list does not get updated, as I'm currently returning false in the $$updated method.

Question: What should go in the $$updated method so that when theres a change in a Post data, my list gets updated accordingly (and further returns the author's name!). Thanks

I think you're going through too many loops to get something simple done.

If the name of the author is "part of" the article than you should save it:

{
    "articles": {
        "firebase-uniq-id-1": {
            "title": "My Writing Process",
            "published": "2016-01-01",
            "author": {
                "firebase-uniq-id-2": "Ernest Hemingway"
            }
        }
    },
    "authors": {
        "firebase-uniq-id-2": {
            "name": "Ernest Hemingway",
            "born": "1899-07-21",
            "whatever": "Some Data"
        }
    }
}

When you'll want to show other details about the author, fetch it.

Edit: If you still wish to use the extension option, I believe the only thing you're missing there is extending the updateRecord with rec:

FirebaseFactory.$getAuthorId( updatedRecord.authorId )
    .$loaded(function( authorData ) { 
        updatedRecord.authorData = authorData; 
        angular.extend(updatedRecord, snap.val());
    });

Also, in $$updated you need to return a boolean saying if the record changed or not, and not the record itself.

Keep in mind that if you go that path you shouldn't use the default $save() method of $firebaseArray since it will also save the full authorData