How to represent arrays within ember-data models?

Well… It was a little bit difficult but mixing all answers in this post I made it work.

Firstly, you should create a transform for the new type “array”:

DS.ArrayTransform = DS.Transform.extend({
  deserialize: function(serialized) {
    return (Ember.typeOf(serialized) == "array")
        ? serialized 
        : [];
  },

  serialize: function(deserialized) {
    var type = Ember.typeOf(deserialized);
    if (type == 'array') {
        return deserialized
    } else if (type == 'string') {
        return deserialized.split(',').map(function(item) {
            return jQuery.trim(item);
        });
    } else {
        return [];
    }
  }
});

App.register("transform:array", DS.ArrayTransform);

Now, in your model, just use it as another attr:

App.myModel = Ember.Model.extend({
    name : DS.attr('string'),
    cont : DS.attr('array')
}

And we are done.
Remember, when adding elements to the array, to use pushObject.

In a controller:

this.get('model.cont').pushObject('new Item');