I'm populating the combo box from a query and the debug shows the correct number of box entries after an add or a delete.
Qt Code: 
  1. void DxSpots::loadClusters()
  2. {
  3.   qDebug() << "Loading clusters";
  4.   ui->cbClusters->clear();
  5.   qDebug() << "combo count 1 = " << ui->cbClusters->count();
  6.   // Load the stored urls into the combo box
  7.   QSqlQuery queryu(::spotsDB);
  8.   queryu.exec("Select url from nodes order by url");
  9.   int i = 0;
  10.   while (queryu.next())
  11.   {
  12.     qDebug() << "url is " << queryu.value(0).toString();
  13.  
  14.     ui->cbClusters->insertItem(i, queryu.value(0).toString());
  15.     i++;
  16.   }
  17.   qDebug() << "combo count 2 = " << ui->cbClusters->count();
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This slot is called each time an add or delete is done from the options form.