Question

I have a Model that looks like:

var Playlist = Backbone.Model.extend({
    defaults: function() {
        return {
            id: null,
            items: new PlaylistItems()
        };
    }
});

where PlaylistItems is a Backbone.Collection.

After I create a Playlist object, I call save.

playlist.save({}, {
    success: function(model, response, options) {
        console.log("model:", model, response, options);
    },
    error: function (error) {
        console.error(error);
    }
});

In here, my model is a Backbone.Model object. However, its child, items, is of type Array and not Backbone.Collection.

This was unexpected behavior. Am I missing something? Or, do I need to manually pass my array into a new Backbone.Collection and initialize this myself?

Answer 1

It kind of depends on what your server is expecting and what it responds with. Backbone does not know that the attribute items is a Backbone Collection and what to do with it. Something like this might work, depending on your server.

 var Playlist = Backbone.Model.extend({
    defaults: function() {
        return {
            id: null,
            items: new PlaylistItems()
        };
    },
    toJSON: function(){
        // return the json your server is expecting.
        var json = Backbone.Model.prototype.toJSON.call(this);
        json.items = this.get('items').toJSON();
        return json;
    },
    parse: function(data){
        // data comes from your server response
        // so here you need to call something like:
        this.get('items').reset(data.items);
        // then remove items from data: 
        delete data.items;
        return data;
    }

});