ttksingleton.h

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#ifndef TTKSINGLETON_H
#define TTKSINGLETON_H

/***************************************************************************
 * This file is part of the TTK Library Module project
 * Copyright (C) 2015 - 2025 Greedysky Studio

 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.

 * You should have received a copy of the GNU Lesser General Public License along
 * with this program; If not, see <http://www.gnu.org/licenses/>.
 ***************************************************************************/

#include <QMutex>
#include <QScopedPointer>
#include "ttkmoduleexport.h"

template <typename T>
class TTK_MODULE_EXPORT TTKSingleton
{
public:
    static T* instance();

private:
    TTKSingleton() = default;
    ~TTKSingleton() = default;

    static QMutex m_mutex;
    static QScopedPointer<T> m_instance;
    TTK_DISABLE_COPY(TTKSingleton)

};


template <typename T> QMutex TTKSingleton<T>::m_mutex;
template <typename T> QScopedPointer<T> TTKSingleton<T>::m_instance;

template <typename T>
T* TTKSingleton<T>::instance()
{
    if(m_instance.isNull())
    {
        m_mutex.lock();
        if(m_instance.isNull())
        {
            m_instance.reset(new T());
        }
        m_mutex.unlock();
    }
    return m_instance.data();
}


#define TTK_DECLARE_SINGLETON_CLASS(Class)       \
    friend class TTKSingleton<Class>;            \
    friend struct QScopedPointerDeleter<Class>;

#endif // TTKSINGLETON_H