qscopedvaluerollback.h

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#ifndef QSCOPEDVALUEROLLBACK_H
#define QSCOPEDVALUEROLLBACK_H
 
#include <QtCore/qglobal.h>
 
QT_BEGIN_NAMESPACE
 
template <typename T>
class QScopedValueRollback
{
public:
    Q_NODISCARD_CTOR
    explicit constexpr QScopedValueRollback(T &var)
        : varRef(var), oldValue(var)
    {
    }
 
    Q_NODISCARD_CTOR
    explicit constexpr QScopedValueRollback(T &var, T value)
        : varRef(var), oldValue(std::move(var)) // ### C++20: std::exchange(var, std::move(value))
    {
        var = std::move(value);
    }
 
#if __cpp_constexpr >= 201907L
    constexpr
#endif
    ~QScopedValueRollback()
    {
        varRef = std::move(oldValue);
    }
 
    constexpr void commit()
    {
        oldValue = varRef;
    }
 
private:
    T &varRef;
    T oldValue;
 
    Q_DISABLE_COPY_MOVE(QScopedValueRollback)
};
 
QT_END_NAMESPACE
 
#endif // QSCOPEDVALUEROLLBACK_H