Unable to connect signal to a function inside main()

Question

I am aware that to use the signals and slots mechanism of Qt inside a class, the class must include the Q_OBJECT macro, but I am attempting to use signals and slots in main(), without using any class.

Here is my code so far:

#include <QApplication>
#include <QWidget>
#include <QTextEdit>
#include <QtGui>

void saveText();

int main(int argv, char **args)
 {
    QApplication app(argv, args);
    QTextEdit textEdit;
    QPushButton saveButton("Save!");
    QPushButton exitButton("Exit!");
    QObject::connect(&exitButton,SIGNAL(clicked()),qApp,SLOT(quit()));
    QObject::connect(&saveButton,SIGNAL(clicked()),qApp,SLOT(saveText()));

    QVBoxLayout vlyt;
    vlyt.addWidget(&textEdit);
    vlyt.addWidget(&exitButton);
    vlyt.addWidget(&saveButton);

    QWidget mainWindow;
    mainWindow.setLayout(&vlyt);
    mainWindow.show();

    return app.exec();
}

void saveText()
{
    exit(0);
}

Here is the GUI window generated:

From the above code, the exit button is connected to quit(), which is a Qt function, when clicked it works. The save button assigned to the function saveText(), is configured to exit, but does not do so.

Please tell me where I have gone wrong in understanding signals and slots in Qt.

Answer 1

Qt4...

All classes that inherit from QObject or one of its subclasses (e.g., QWidget) can contain signals and slots.¹

So, you can not use slots where placed outside of QObject children.

You can connect signals to the slots which are in classes where derived from QObject. Put your slot in a class which is in a separated .h/.cpp file:

class MyClass : public QObject
{
   Q_OBJECT

   ...

   public slots:
     void saveText();

};

According to Qt5: New Signal Slot Syntax in Qt 5. You can connect to those type of global functions. (Thanks to @thuga's comments)