title: How to refresh contents of QCombobox in QTableView
body: <p>I have QTableView which has QComboBox in one of the columns. The combobox is displaying data from a vector which get updates when I click a button. 
  When I start the application the combobox displays all the items in vector. Now I press  the button (which adds more items to the vector) but the combobox doesn't reflect new data in vector. It still shows old data. I am also emitting dataChanged() once the vector is updated but I don't see any change. data() function does get call in the model which does return all the elements of the vector, but setEditorData doesn't get call in delegate. </p>
  
  <p>Am I missing something.</p>
  
  <p>Thanks,</p>
  
  <p>Dev</p>