title: Add QObject in the combo box of Qt
body: <p>I have a custom class I created, say MyClass. Now how to add a reference to MyClass's reference as second parameter in the combo box below:</p>
  
  <p>this->ui->comboBox->addItem("item-1", );</p>
  
  <p>Purpose is to when item changed even is fired, i want to get that specific class instance of MyClass and process accordingly.</p>