KisValueCache.h

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/*
 *  SPDX-FileCopyrightText: 2023 Dmitry Kazakov <dimula73@gmail.com>
 *
 *  SPDX-License-Identifier: GPL-2.0-or-later
 */
 
#ifndef KISVALUECACHE_H
#define KISVALUECACHE_H
 
#include <optional>
 
template <typename Initializer>
struct KisValueCache : Initializer
{
    using value_type = decltype(std::declval<Initializer>().initialize());
 
    template <typename ...Args>
    KisValueCache(Args... args)
        : Initializer(args...)
    {
    }
 
    const value_type& value() {
        if (!m_value) {
            m_value = Initializer::initialize();
        }
 
        return *m_value;
    }
 
    operator const value_type&() const {
        return value();
    }
 
    bool isValid() const {
        return bool(m_value);
    }
 
    void clear() {
        m_value = std::nullopt;
    }
 
private:
    std::optional<value_type> m_value;
};
 
#endif // KISVALUECACHE_H