The change of data in controller doesn't update automatically

Thanks for your reminding. Then can do it even better with:

return new Promise((resolve, reject) => {
  window.imagePicker.getPictures((results) => {
    for (var i = 0; i < results.length; i++ ) {
      this.thumbnail = results[i]
      return resolve(result[i]);
    }
  }, (error) => {
    return reject(error);
  });
}

Am I right?