single demo

/****************************************************************************
** 
** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
** 
** This file is part of a Qt Solutions component.
**
** Commercial Usage  
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Solutions Commercial License Agreement provided
** with the Software or, alternatively, in accordance with the terms
** contained in a written agreement between you and Nokia.
** 
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
** 
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
** package.
** 
** GNU General Public License Usage 
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
** 
** Please note Third Party Software included with Qt Solutions may impose
** additional restrictions and it is the user's responsibility to ensure
** that they have met the licensing requirements of the GPL, LGPL, or Qt
** Solutions Commercial license and the relevant license of the Third
** Party Software they are using.
** 
** If you are unsure which license is appropriate for your use, please
** contact Nokia at qt-info@nokia.com.
** 
****************************************************************************/
 
 
#include "qtsinglecoreapplication.h"
#include <QtCore/QDebug>
 
 
void report(const QString& msg)
{
    qDebug("[%i] %s", (int)QCoreApplication::applicationPid(), qPrintable(msg));
}
 
class MainClass : public QObject
{
    Q_OBJECT
public:
    MainClass()
        : QObject()
        {}
 
public slots:
    void handleMessage(const QString& message)
        {
            report( "Message received: \"" + message + "\"");
        }
};
 
int main(int argc, char **argv)
{
    report("Starting up");
 
    QtSingleCoreApplication app(argc, argv);
 
    if (app.isRunning()) {
        QString msg(QString("Hi master, I am %1.").arg(QCoreApplication::applicationPid()));
        bool sentok = app.sendMessage(msg);
        QString rep("Another instance is running, so I will exit.");
        rep += sentok ? " Message sent ok." : " Message sending failed.";
        report(rep);
        return 0;
    } else {
        report("No other instance is running; so I will.");
        MainClass mainObj;
        QObject::connect(&app, SIGNAL(messageReceived(const QString&)),
                         &mainObj, SLOT(handleMessage(const QString&)));
        return app.exec();
    }
}
 
 
#include "main.moc"