Editing problem in QTreeView

I have a QTreeView in my application. When user double clicks on an item to edit it's value, the value disappears and user finds himself/herself in a line-edit like something with no text at all. I want the user to be able to edit the text inside the item, without destroying it (i mean i want the user to see the text he is editing at the time of editing.) How can I do that?

I think you need to be sure the override of QAbstractItemModel::data in your model returns the text to be edited when asked for the Qt::EditRole

are you using custom delegate?