StateMachine Ping Pong Example

The Ping Pong States example shows how to use parallel states together with custom events and transitions in The State Machine Framework. It corresponds to the Qt example Ping Pong States Example.

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ping_pong.py

# Copyright (C) 2010 velociraptor Genjix <aphidia@hotmail.com>
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

import sys

from PySide6.QtCore import QCoreApplication, QEvent
from PySide6.QtStateMachine import QAbstractTransition, QState, QStateMachine


class PingEvent(QEvent):
    def __init__(self):
        super().__init__(QEvent.Type(QEvent.User + 2))


class PongEvent(QEvent):
    def __init__(self):
        super().__init__(QEvent.Type(QEvent.User + 3))


class Pinger(QState):
    def __init__(self, parent):
        super().__init__(parent)

    def onEntry(self, e):
        self.p = PingEvent()
        self.machine().postEvent(self.p)
        print('ping?')


class PongTransition(QAbstractTransition):
    def eventTest(self, e):
        return e.type() == QEvent.User + 3

    def onTransition(self, e):
        self.p = PingEvent()
        machine.postDelayedEvent(self.p, 500)
        print('ping?')


class PingTransition(QAbstractTransition):
    def eventTest(self, e):
        return e.type() == QEvent.User + 2

    def onTransition(self, e):
        self.p = PongEvent()
        machine.postDelayedEvent(self.p, 500)
        print('pong!')


if __name__ == '__main__':
    app = QCoreApplication(sys.argv)

    machine = QStateMachine()
    group = QState(QState.ParallelStates)
    group.setObjectName('group')

    pinger = Pinger(group)
    pinger.setObjectName('pinger')
    pinger.addTransition(PongTransition())

    ponger = QState(group)
    ponger.setObjectName('ponger')
    ponger.addTransition(PingTransition())

    machine.addState(group)
    machine.setInitialState(group)
    machine.start()

    sys.exit(app.exec())