relationships using DS.Store#filter

gistfile1.js

App.FirstModel = DS.Model.extend({
  foreignUnsorted: function() {
    return App.store.filter(App.ForeignModel, function(hash) {
      return false;
    });
  }.property().cacheable(),
  foreign: function() {
    var foreignUnsorted = this.get('foreignUnsorted');

    return foreignUnsorted.toArray().sort(function(a,b) {
      return a.get('sortProperty') - b.get('sortProperty');
    });
  }.property('foreignUnsorted.@each').cacheable(),
  isLoadedDidChange: function() {
    var id = this.get('id');
    if (!id) return;
    if (this._filterFunctionsSet) return;
    this.setPath('foreignUnsorted.filterFunction', function(hash) {
      return hash.other_id === id;
    });
    this._filterFunctionsSet = true;
  }.observes('isLoaded','id'),
});