public function __construct($attributes = array()){

    $this->path = url('img/' . $this->{'file-name'});
    parent::__construct($attributes);

}

{
  id: 25,
  text: "A lovely file",
  file-name: "file.jpg",
  created_at: "2016-02-12 11:44:37",
  updated_at: "2016-02-12 11:44:37"
},

{
  id: 25,
  text: "A lovely file",
  file-name: "file.jpg",
  path: "http://myapp.app:8000/img/file.jpg",
  created_at: "2016-02-12 11:44:37",
  updated_at: "2016-02-12 11:44:37"
},