TrafficLightController.hpp Example File

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    #ifndef TRAFFICLIGHTCONTROLLER_HPP
    #define TRAFFICLIGHTCONTROLLER_HPP

    #include <QObject>

    class QTimer;

    /**
     * TrafficLightController
     *
     * The class that contains the business logic of the application.
     * It represents a traffic light that automatically switches between the three
     * colors red, yellow and green.
     * The control flow is orchestrated by a QStateMachine, which can be paused in
     * execution.
     * The states of the single lights of the traffic light are made available via
     * properties, so that the UI can bind against them directly.
     */
    class TrafficLightController : public QObject
    {
        Q_OBJECT

        // the state properties for the single lights
        Q_PROPERTY(bool redOn READ redOn WRITE setRedOn NOTIFY redOnChanged)
        Q_PROPERTY(bool yellowOn READ yellowOn WRITE setYellowOn NOTIFY yellowOnChanged)
        Q_PROPERTY(bool greenOn READ greenOn WRITE setGreenOn NOTIFY greenOnChanged)

        // the state property that reflects whether the traffic light is currently paused
        Q_PROPERTY(bool paused READ paused WRITE setPaused NOTIFY pausedChanged)

    public:
        TrafficLightController(QObject *parent = 0);

        // accessor methods for the state properties
        bool redOn() const;
        void setRedOn(bool on);

        bool yellowOn() const;
        void setYellowOn(bool on);

        bool greenOn() const;
        void setGreenOn(bool on);

        bool paused() const;
        void setPaused(bool paused);

    public Q_SLOTS:
        /**
         * This slot is called by the UI to pause/continue the traffic light
         */
        void pause();

    Q_SIGNALS:
        // change notification signals for the state properties
        void redOnChanged();
        void yellowOnChanged();
        void greenOnChanged();
        void pausedChanged();

        /**
         * This signal is emitted when the pause() slot is invoked and is used
         * by the internal state machine only.
         */
        void pauseRequested();

    private:
        /**
         * Creates the internal state machine.
         */
        void setupStateMachine();

        // state property variables
        bool m_redOn;
        bool m_yellowOn;
        bool m_greenOn;
        bool m_paused;

        // the timer that triggers the state changes
        QTimer *m_timer;
    };

    #endif