QMainWindow same value of widget->metaObject()->className() and widget->objectName()

[tonnot]

I have the same value for :
widget->metaObject()->className()
widget->objectName()
The widget is a QMainWindow, I'm trying to distinguish betwen QMainWindow and other Qdialogs, but in case of the widget was a QMainWindow I have "Ui_main" for both.
Any help ?
Thanks.