Passing QSpinBox::value() to a gloabal variable

[adonis]

I have connected the QSpinBox::valueChanged() Signal to a slot from my QMainMindow class.This is a part of the code:

double dimx;//The global scope
...
void MainWindow::accepter(double d){
       dimx=d; 
qApp->aboutQt();
}
//in the main function
...
      QApplication app(argc, argv);
      MainWindow *mainWin=new MainWindow;
    std:: ofstream myfile;
 
      myfile.open ("data.txt");
         myfile<<dimx;
       myfile.close();
 
 
       return app.exec();
}

double dimx;//The global scope
...
void MainWindow::accepter(double d){
       dimx=d; 
qApp->aboutQt();
}
//in the main function
...
      QApplication app(argc, argv);
      MainWindow *mainWin=new MainWindow;
    std:: ofstream myfile;

      myfile.open ("data.txt");
         myfile<<dimx;
       myfile.close();


       return app.exec();
}

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The qApp->aboutQt() make sure that the Signal /slot connection works.
What i get in my data.txt file is the initial value of dimx.