Question

I am following the Qt example listed in the QtSDK titled: “Getting Started Programming with Qt”. My problem is that the program doesn’t display any of the objects.

My main.cpp looks like so:

#include <QtGui>

#include <notepad.h>

int main(int argv, char **args)  {
    QApplication app(argv, args);

    QVBoxLayout layout;

    Notepad notepad();

    QWidget window;
    window.setLayout(&layout);

    window.show();

    return app.exec();
}

The ‘notepad.h’ file:

#ifndef NOTEPAD_H
#define NOTEPAD_H

#include <QtGui>

class Notepad : public QMainWindow  {
    Q_OBJECT

    public:
        Notepad();

    private slots:
        void open();
        void save();
        void quit();

    private:
        QTextEdit *text_edit;

        QAction *open_action;
        QAction *save_action;
        QAction *exit_action;

        QMenu *file_menu;
};

#endif // NOTEPAD_H

The ‘notepad.cpp’ file:

#include "notepad.h"

Notepad::Notepad()  {
    open_action = new QAction(tr("&Open"), this);
    save_action = new QAction(tr("&Save"), this);
    exit_action = new QAction(tr("&Exit"), this);

    connect(open_action, SIGNAL(triggered()), this, SLOT(open()));
    connect(save_action, SIGNAL(triggered()), this, SLOT(save()));
    connect(exit_action, SIGNAL(triggered()), qApp, SLOT(quit()));

    file_menu = menuBar()->addMenu(tr("&File"));
    file_menu->addAction(open_action);
    file_menu->addAction(save_action);
    file_menu->addSeparator();
    file_menu->addAction(exit_action);

    text_edit = new QTextEdit;
    setCentralWidget(text_edit);

    setWindowTitle(tr("Notepad"));
}

void Notepad::open()  {
    ...
}

void Notepad::save()  {
    ...
}

void Notepad::quit()  {
}

Any help in resolving the matter would be much appreciated.

Edit

My original question asked why I was I was getting a compile time error for not implementing the “quit” function incase you are wondering :).

Answer 1

You have to implement quit() method defined as private slot in notepad.h . Unresolved errors are linking errors and tells you that linker hasn’t found any implementation for the function declaration. Add this to notepad.cpp :

void Notepad::quit()  {
    ...
}

For new question :

Try notepad.show(). Your MainWindow can be notepad object because it is a QMainWindow.

int main(int argv, char **args)  {
    QApplication app(argv, args);

    Notepad notepad();
    notepad.show();

    return app.exec();
}