title: How to update value inside shared preferences in flutter
body: <p>actually when saving data inside shared preferences.. I am using this code</p>
  
  <pre><code>add() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setString('data', "ok");
  }
  </code></pre>
  
  <p>but, is there a way to update the value of <code>data</code> for example I want to change <code>ok</code> into <code>fine</code>
  because when I try to re-save my data using that code... and call it using <code>prefs.getString('data');</code> it always shows the old data not the update one</p>