Backbone.js Collection of Collections

Question

I'm trying to figure out how to make a Collection of collections with backbone.js. I'm pretty new to backbone. I have something like the following situation:

 +---------------+               +------------------+  | Playlists     |               | Playlist         |  |---------------|          0..* |------------------|  |               +-------------->| Name             |  |               |               |                  |  |               |               |                  |  +---------------+               +-------+----------+                                          |                                          |                                          |0..*                                          v                                  +------------------+                                  |  Track           |                                  |------------------|                                  | Name             |                                  | Artist           |                                  |                  |                                  +------------------+ 

In code this looks similar to this:

var trackModel = Backbone.Model.extend({     //trackdata });  var playlistModel = Backbone.Collection.extend({     model : trackModel,     url   : "playlist" });  var playlistsModel = Backbone.Collection.extend({     url   : "playlists",     model : playlistModel   //This pretty sure doesn't work like I want, because there is no model attribute for collections :S }); 

However I always receive an error in the js console saying:

 Uncaught TypeError: Object [object Object] has no method '_validate' 

when I try to execute a function that triggers the validate (like add, fetch, ...)

It makes no difference if i add the validate or _validate function to any of the collections or models.

I believe this is because backbone.js doesn't support collections in collections. Is there another way that works?

UPDATE:

This is how it looks right now

var Track = Backbone.Model.extend({      //trackdata  });   var Tracks = Backbone.Collection.extend({      model:Track;  });   var Playlist = Backbone.Model.extend({      //name  : ...     tracks: new Tracks () });   var Playlists = Backbone.Collection.extend({      url : "playlists",      model : Playlist  }); 

Answer 1

You'd solve your problem by turning your Playlist from a collection into a model. If you think about it, a Playlist would probably have other attributes anyway (e.g. name) that wouldn't be settable on a collection.

Playlists would then be a collection of Playlist models (instead of collections), which should work without error.

var Track = Backbone.Model.extend({     //trackdata });  var Playlist = Backbone.Model.extend({     model : Track });  var Playlists = Backbone.Collection.extend({     url   : "playlists",     model : Playlist });