On my application I try to retrieve data from a database. If this step is succesfull the application continues, Instead I want that the application shows a QMessage::critical(...) and closes with QApplication::exit(). The error appears but the application dosn't stops. The code is:

Qt Code: 
  1. wMain::wMain(QWidget *parent) : QWidget(parent), ui(new Ui::wMain)
  2. {
  3.     ui->setupUi(this);
  4.     this->actualizarInterfaz();
  5. }
  6.  
  7. void wMain::actualizarInterfaz()
  8. {
  9.         DAO* aDao = new DAO("");
  10.         this->asg = aDao->Query(1);
  11.         delete aDao;
  12.  
  13.         if(this->asg != NULL)
  14.         {
  15.             // populate gui with data recovered
  16.         }
  17.         else
  18.         {
  19.             QMessageBox::critical(
  20.                     this,
  21.                     "Error",
  22.                     "...");
  23.             qApp->exit(1);
  24.         }
  25. }
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How could I fix this? There are another ways to do it?