qgsoptional.h

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/***************************************************************************
  qgsoptional.h - QgsOptional
 
 ---------------------
 begin                : 7.9.2016
 copyright            : (C) 2016 by Matthias Kuhn
 email                : matthias@opengis.ch
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
#ifndef QGSOPTIONAL_H
#define QGSOPTIONAL_H
 
#include "qgis_core.h"
#include "qgis_sip.h"

template<typename T> class CORE_EXPORT QgsOptional
{
  public:
    QgsOptional() = default;

    QgsOptional( const T &data )
      : mEnabled( true )
      , mData( data )
    {}

    QgsOptional( const T &data, bool enabled )
      : mEnabled( enabled )
      , mData( data )
    {}

    bool operator==( const QgsOptional<T> &other ) const { return mEnabled == other.mEnabled && mData == other.mData; }

    explicit operator bool() const SIP_SKIP { return mEnabled; }

    bool enabled() const { return mEnabled; }

    void setEnabled( bool enabled ) { mEnabled = enabled; }

    const T *operator->() const { return &mData; }

    T data() const { return mData; }

    void setData( const T &data ) { mData = data; }
 
  private:
    bool mEnabled = false;
    T mData;
};
 
// These typedefs are in place to work around a SIP bug:
// https://github.com/Python-SIP/sip/issues/66
#ifndef SIP_RUN
#include "qgsexpression.h"
typedef QgsOptional<QgsExpression> QgsOptionalQgsExpressionBase;
#endif
 
#endif // QGSOPTIONAL_H