main.cpp Example File

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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)
      {}

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

      void onTransition(QEvent *e) 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)
      {}

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

      void onTransition(QEvent *) 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"