title: Force computed.filter() to update?
body: <p>I've got a filter that works <em>once</em>, with whatever values are pre-initialized in, just at initial initiazation, but never updates.  editstate is a service; in this case it just provides those exposed variables.  So the idea is that when editstate.filterValue and editstate.filterField are changed, the filter should update.</p>
  
  <p>But it doesn't.  </p>
  
  <p>I've tried having them be local computed values also, but no dice.  The only programmatic thing that works so far is to unrender and rerender the entire component using a handlebars {{#if toggle.</p>
  
  <pre><code>export default Ember.Component.extend({
      store: Ember.inject.service(),
      editstate: Ember.inject.service('edit-state'),
      filteredList: Ember.computed.filter('model', function(current, index, all) {
              return current.get(Ember.get(this.get('editstate'), 'filterField')) == Ember.get(this.get('editstate'), 'filterValue');
      }),
  </code></pre>
  
  <p>What am I missing?  I don't see any API for forcing a filter to re-compute, nor to tell it more explicitly to watch these values.  </p>
  
  <p><strong>Update</strong>: I found a <em>terrible hacky way</em> to accomplish my goal: In my service, I create <em>but don't save</em> a record in the model that I'm filtering, just to force updates.  Whenever the filter parameters change, I update that record with the current time (millis).  And of course it's always filtered out by the filter.  </p>
  
  <p>It's ugly, it's probably evil... is there a better way?</p>