singleton.h

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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#ifndef SINGLETON_H
#define SINGLETON_H
 
#include <QtQml/qobject.h>
#include <QtQml/qqml.h>
#include <QtQml/qqmlengine.h>
 
// Singleton.h
class Singleton : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int thing READ thing WRITE setThing NOTIFY thingChanged FINAL)
    QML_ELEMENT
    QML_SINGLETON
 
public:
    Singleton(QObject *parent = nullptr) : QObject(parent) {}
 
    int thing() const { return m_value; }
    void setThing(int v)
    {
        if (v != m_value) {
            m_value = v;
            emit thingChanged();
        }
    }
 
signals:
    void thingChanged();
 
private:
    int m_value = 12;
};
 
inline void setTheThing(QQmlEngine *engine)
{
    Singleton *singleton
            = engine->singletonInstance<Singleton *>("MyModule", "Singleton");
    singleton->setThing(77);
}
 
#endif