- Qt 5.5
- Qt Widgets
- Factorial States Example
- main.cpp Example File
- Qt 5.5.1 Reference Documentation

# main.cpp Example File

statemachine/factorial/main.cpp

    /****************************************************************************
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    ** 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:
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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) Q_DECL_OVERRIDE
        {
            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) Q_DECL_OVERRIDE
        {
            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) Q_DECL_OVERRIDE
        {
            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 *) Q_DECL_OVERRIDE
        {
            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"