Hi can you give the whole code ?
What you do in response to a dataChanged() signal is specific to your application. Any "whole code" for this thread would probably have no meaning in your application.

I suggest you start with reading about Qt Model/View Programming in the documentation, look at the Model/View tutorial, and finally look at some of the 19 examples of Model/View programming that come with Qt.

You will probably learn enough in that to understand how to use the QAbstractItemModel::dataChanged() signal in your own application.