refs #873, nullable interface for value objects

src/blackmisc/nullable.h

@@ -0,0 +1,60 @@
+/* Copyright (C) 2017
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_NULLABLE_H
+#define BLACKMISC_NULLABLE_H
+
+#include "blackmisc/blackmiscexport.h"
+#include "blackmisc/propertyindex.h"
+#include "blackmisc/variant.h"
+
+namespace BlackMisc
+{
+    //! Nullable value object
+    class BLACKMISC_EXPORT INullable
+    {
+    public:
+        //! Properties by index
+        enum ColumnIndex
+        {
+            IndexIsNull = BlackMisc::CPropertyIndex::GlobalIndexINullable,
+        };
+
+        //! Constructor, init to null
+        INullable(std::nullptr_t null);
+
+        //! Null?
+        bool isNull() const { return m_isNull; }
+
+        //! Null?
+        void setNull(bool null) { m_isNull = null; }
+
+        //! Can given index be handled
+        static bool canHandleIndex(const BlackMisc::CPropertyIndex &index);
+
+    protected:
+        //! Constructor
+        INullable() {}
+
+        //! \copydoc BlackMisc::Mixin::Index::propertyByIndex
+        CVariant propertyByIndex(const BlackMisc::CPropertyIndex &index) const;
+
+        //! \copydoc BlackMisc::Mixin::Index::setPropertyByIndex
+        void setPropertyByIndex(const BlackMisc::CPropertyIndex &index, const CVariant &variant);
+
+        //! Compare for index
+        int comparePropertyByIndex(const CPropertyIndex &index, const INullable &compareValue) const;
+
+        bool m_isNull = false; //!< null?
+    };
+} // namespace
+
+#endif // guard