XdlOrm/include/QxExtras/QxStdOptional.h

/****************************************************************************
**
** https://www.qxorm.com/
** Copyright (C) 2013 XDL Team (ic-east.com)
**
** This file is part of the QxOrm library
**
** This software is provided 'as-is', without any express or implied
** warranty. In no event will the authors be held liable for any
** damages arising from the use of this software
**
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** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and XDL Team
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file 'license.gpl3.txt' included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met : http://www.gnu.org/copyleft/gpl.html
**
** If you are unsure which license is appropriate for your use, or
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#ifndef _QX_STD_OPTIONAL_H_
#define _QX_STD_OPTIONAL_H_

#ifdef _MSC_VER
#pragma once
#endif

/*!
 * \file QxStdOptional.h
 * \author XDL Team
 * \ingroup QxExtras
 * \brief Support std::optional<T> class (requires a C++17 compiler) to manage NULL database value, this header should be included just after <QxOrm.h> header file (ideally in a precompiled header)
 */

#include <optional>

#include <QtCore/qdatastream.h>

#include <QxOrm.h>

#include <QxTraits/construct_null_qvariant.h>

template <typename T>
QDataStream &operator<<(QDataStream &stream, const std::optional<T> &t)
{
   qint8 iHasData = (t ? 1 : 0);
   stream << iHasData;
   if (t)
   {
      stream << (*t);
   }
   return stream;
}

template <typename T>
QDataStream &operator>>(QDataStream &stream, std::optional<T> &t)
{
   qint8 iHasData = 0;
   stream >> iHasData;
   if (iHasData)
   {
      t = T();
      stream >> (*t);
   }
   else
   {
      t = std::optional<T>();
   }
   return stream;
}

QX_REGISTER_CLASS_NAME_TEMPLATE_1(std::optional)

namespace qx
{
   namespace trait
   {

      template <typename T>
      struct get_sql_type<std::optional<T>>
      {
         static inline const char *get() { return qx::trait::get_sql_type<T>::get(); }
      };

   } // namespace trait
} // namespace qx

namespace qx
{
   namespace cvt
   {
      namespace detail
      {

#ifndef _QX_NO_JSON

         template <typename T>
         struct QxConvert_ToJson<std::optional<T>>
         {
            static inline QJsonValue toJson(const std::optional<T> &t, const QString &format)
            {
               if (t)
               {
                  return qx::cvt::to_json((*t), format);
               };
               return QJsonValue();
            }
         };

         template <typename T>
         struct QxConvert_FromJson<std::optional<T>>
         {
            static inline qx_bool fromJson(const QJsonValue &j, std::optional<T> &t, const QString &format)
            {
               if (j.isNull())
               {
                  t = std::optional<T>();
                  return qx_bool(true);
               }
               else if (!t)
               {
                  t = T();
               }
               return qx::cvt::from_json(j, (*t), format);
            }
         };

#endif // _QX_NO_JSON

         template <typename T>
         struct QxConvert_ToString<std::optional<T>>
         {
            static inline QString toString(const std::optional<T> &t, const QString &format, int index, qx::cvt::context::ctx_type ctx)
            {
               if (t)
               {
                  return qx::cvt::to_string((*t), format, index, ctx);
               };
               return QString();
            }
         };

         template <typename T>
         struct QxConvert_FromString<std::optional<T>>
         {
            static inline qx_bool fromString(const QString &s, std::optional<T> &t, const QString &format, int index, qx::cvt::context::ctx_type ctx)
            {
               if (!t)
               {
                  t = T();
               };
               return qx::cvt::from_string(s, (*t), format, index, ctx);
            }
         };

         template <typename T>
         struct QxConvert_ToVariant<std::optional<T>>
         {
            static inline QVariant toVariant(const std::optional<T> &t, const QString &format, int index, qx::cvt::context::ctx_type ctx)
            {
               if (t)
               {
                  return qx::cvt::to_variant((*t), format, index, ctx);
               };
               return qx::trait::construct_null_qvariant<T>::get();
            }
         };

         template <typename T>
         struct QxConvert_FromVariant<std::optional<T>>
         {
            static inline qx_bool fromVariant(const QVariant &v, std::optional<T> &t, const QString &format, int index, qx::cvt::context::ctx_type ctx)
            {
               if (v.isNull())
               {
                  t = std::optional<T>();
                  return qx_bool(true);
               }
               else if (!t)
               {
                  t = T();
               }
               return qx::cvt::from_variant(v, (*t), format, index, ctx);
            }
         };

      } // namespace detail
   } // namespace cvt
} // namespace qx

#endif // _QX_STD_OPTIONAL_H_