title: QT - Fill a QMap with only key, and then add values for each key
body: <p>I would like to know if is it possible to fill a QMap with only key, and then for each key add value.</p>
  
  <p>for example, something like :</p>
  
  <pre><code>QMap&lt;QString, QString&gt; map;
  map.insert("key", null (??));
  </code></pre>
  
  <p>Thanks for your answer</p>