How to solve "QWidget: Cannot create a QWidget without QApplication" problem?

Question

Qt

Hello!
The error occurs as soon as it comes to:
QMessageBox msgBox;
QMessageBox is not digested at all.
As I understand it, this is directly related to the fact that the QML project.
How to fix? Or how notifications are displayed in this case?

Answer 1

Create QApplication? What is there in main.cpp in general?