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# main.cpp Example File

statemachine/factorial/main.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2015 The Qt Company Ltd.
     ** Contact: http://www.qt.io/licensing/
     **
     ** This file is part of the QtCore module of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
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     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
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     **     contributors may be used to endorse or promote products derived
     **     from this software without specific prior written permission.
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     #include <QtCore>
     #include <stdio.h>

     class Factorial : public QObject
     {
         Q_OBJECT
         Q_PROPERTY(int x READ x WRITE setX)
         Q_PROPERTY(int fac READ fac WRITE setFac)
     public:
         Factorial(QObject *parent = 0)
             : QObject(parent), m_x(-1), m_fac(1)
         {
         }

         int x() const
         {
             return m_x;
         }

         void setX(int x)
         {
             if (x == m_x)
                 return;
             m_x = x;
             emit xChanged(x);
         }

         int fac() const
         {
             return m_fac;
         }

         void setFac(int fac)
         {
             m_fac = fac;
         }

     Q_SIGNALS:
         void xChanged(int value);

     private:
         int m_x;
         int m_fac;
     };

     class FactorialLoopTransition : public QSignalTransition
     {
     public:
         FactorialLoopTransition(Factorial *fact)
             : QSignalTransition(fact, SIGNAL(xChanged(int))), m_fact(fact)
         {}

         virtual bool eventTest(QEvent *e)
         {
             if (!QSignalTransition::eventTest(e))
                 return false;
             QStateMachine::SignalEvent *se = static_cast<QStateMachine::SignalEvent*>(e);
             return se->arguments().at(0).toInt() > 1;
         }

         virtual void onTransition(QEvent *e)
         {
             QStateMachine::SignalEvent *se = static_cast<QStateMachine::SignalEvent*>(e);
             int x = se->arguments().at(0).toInt();
             int fac = m_fact->property("fac").toInt();
             m_fact->setProperty("fac",  x * fac);
             m_fact->setProperty("x",  x - 1);
         }

     private:
         Factorial *m_fact;
     };

     class FactorialDoneTransition : public QSignalTransition
     {
     public:
         FactorialDoneTransition(Factorial *fact)
             : QSignalTransition(fact, SIGNAL(xChanged(int))), m_fact(fact)
         {}

         virtual bool eventTest(QEvent *e)
         {
             if (!QSignalTransition::eventTest(e))
                 return false;
             QStateMachine::SignalEvent *se = static_cast<QStateMachine::SignalEvent*>(e);
             return se->arguments().at(0).toInt() <= 1;
         }

         virtual void onTransition(QEvent *)
         {
             fprintf(stdout, "%d\n", m_fact->property("fac").toInt());
         }

     private:
         Factorial *m_fact;
     };

     int main(int argc, char **argv)
     {
         QCoreApplication app(argc, argv);
         Factorial factorial;
         QStateMachine machine;

         QState *compute = new QState(&machine);
         compute->assignProperty(&factorial, "fac", 1);
         compute->assignProperty(&factorial, "x", 6);
         compute->addTransition(new FactorialLoopTransition(&factorial));

         QFinalState *done = new QFinalState(&machine);
         FactorialDoneTransition *doneTransition = new FactorialDoneTransition(&factorial);
         doneTransition->setTargetState(done);
         compute->addTransition(doneTransition);

         machine.setInitialState(compute);
         QObject::connect(&machine, SIGNAL(finished()), &app, SLOT(quit()));
         machine.start();

         return app.exec();
     }

     #include "main.moc"