Stumped on save behavior using belongsTo

[brancusi]

I am trying to create a simple relationship between items, units, and conversions. For some reason, when I create the reverse, "belongsTo" on the model, it doesn't save the references.

So I am trying to create a relationship as follows:

Conversion Model

export default DS.Model.extend({
    order: DS.attr('number'),
    quantity: DS.attr('number'),
    unit: DS.belongsTo('unit', { async: true }),
    item: DS.belongsTo('item', { async: true })
})

For some reason if I put the reverse "belongsTo" on the Conversion model, it won't save to the conversions array. If I remove it, it works. Results are below.

Unit Model

export default DS.Model.extend({
    name: DS.attr('string'),
    gramMultiplier: DS.attr('number'),
    conversions: DS.hasMany('conversion', { async: true })
})

Item Model

export default DS.Model.extend({
    name: DS.attr('string'),
    cost: DS.attr('number'),
    conversions: DS.hasMany('conversion', { async: true })
});

Item Index Controller

var Promise = Ember.RSVP.Promise;

export default Ember.ArrayController.extend({
    newItemName:'Straight torture son!',
    unitTypes:null,

    actions: {
        createItem:function(){
            var item = this.store.createRecord('item', {name:this.get('newItemName'), cost:1});
            var conversion = this.store.createRecord('conversion', {item:item, order:0, quantity:1, unit:this.get('unitTypes').objectAt(0)});

            var promiseCollection = [item.save(), conversion.save()];

            this.set('newItemName', '');

            Ember.RSVP.all(promiseCollection).then(function(fulfilled){
                Promise.cast(item.get('conversions')).then(function(conversions){
                    conversions.addObject(conversion);
                    item.save();
                });
            });
        }
    },
});

Firebase - Without belongsTo refs on the Conversion model

{
    -JKxfFa2G9TDkZ5mM-S8: {
        cost: 1,
        conversions: {
            -JKxfFa4MGiZI9P-hQCi: true
        },
        name: "Straight torture son!"
    }
}

Firebase - WITH belongsTo refs on the Conversion model

{
    -JKxa6nDwGVZtzDMNdsd: {
        cost: 1,
        name: "Straight torture son!"
    }
}

Questions

1. I am going off of the article https://www.firebase.com/blog/2013-04-12-denormalizing-is-normal.html - Does this pretty much still stand? Is the preferred method to leave dangling references?
2. Is there a better way to grab a hasMany array to fill? Rather than: Promise.cast(item.get('conversions'))

[aputinski]

@brancusi I'll try to take a look this week. Thanks for all the context!

[rickharrison]

I also had this issue and taking out the belongsTo fixed it for now.

For #2, I think that you can just do item.get('conversions').then(function() {...})

[neverfox]

I'm having the exact same problem, with the exact same "fix." I'm new to the library as of today (coming from Fireplace), but I imagine this has to be a relatively new bug (assuming that's what it is), given that this is a pretty common scenario that wouldn't have gone unnoticed all the way to a 1.x.x release. It took me all of an hour to run into it. Let me know if I can help try out different scenarios.

[neverfox]

I should ask, is it more idiomatic to set the belongsTo objects when creating those records (item and unit on the conversion record) and before doing the addObject, like in @brancusi's example? Or to create the record without them, do the addObject, and then all the saves last? Both approaches seem to give identical results.

[neverfox]

The problem is in ember-data's JSONSerializer here. The only types of relationships that it serializes (1.0.0-beta7) are manyToNone (which is why it works when you drop the belongsTo) and manyToMany. Without the serialized JSON, you won't get the saved references. I don't know if it has always been like this without searching though the commits.

[neverfox]

According to the notes on the commit for this method, it was the intention of the developers that you would have to override it if you needed to save the ids on the hasMany side. We're not the first to be surprised. It looks like emberfire will have to override this method.

[brancusi]

@neverfox nice find! Thank you!

[neverfox]

You're welcome. I was in a bind myself, so I needed it to work. Hopefully, the pull request I submitted is acceptable.

[brancusi]

I hope so too.

[brancusi]

Works thank you!