Observing parent controller model changes to reset content

gistfile1.js

App.CommentsNewController = Em.ObjectController.extend({
  // create an empty comment when this controller is first created, and when its parent controller changes its model
  createNewComment: function () {
    this.set('model', DS.Comment.create()); // I don't use Ember Data so this might not be correct
  }.on('init').observes('parentController.model'), // `parentController` is a relationship set up by `render`
  
  actions: {
    save: function () {
      var comment = this.get('model');
      comment.save();
    }
  }
});