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#include <QtCore>

#include <stdio.h>

//! [0]

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;

};

//! [0]

//! [1]

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;

};

//! [1]

//! [2]

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;

};

//! [2]

//! [3]

int main(int argc, char **argv)

{

    QCoreApplication app(argc, argv);

    Factorial factorial;

    QStateMachine machine;

//! [3]

//! [4]

    QState *compute = new QState(&machine);

    compute->assignProperty(&factorial, "fac", 1);

    compute->assignProperty(&factorial, "x", 6);

    compute->addTransition(new FactorialLoopTransition(&factorial));

//! [4]

//! [5]

    QFinalState *done = new QFinalState(&machine);

    FactorialDoneTransition *doneTransition = new FactorialDoneTransition(&factorial);

    doneTransition->setTargetState(done);

    compute->addTransition(doneTransition);

//! [5]

//! [6]

    machine.setInitialState(compute);

    QObject::connect(&machine, SIGNAL(finished()), &app, SLOT(quit()));

    machine.start();

    return app.exec();

}

//! [6]

#include "main.moc"