Issue #77 Add class CPropertyIndexRef

This is a reference to a CPropertyIndex with
a subset of its API, and fewer dependencies.

src/blackmisc/propertyindexref.h

@@ -0,0 +1,114 @@
+/* Copyright (C) 2013
+ * 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. 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_PROPERTYINDEXREF_H
+#define BLACKMISC_PROPERTYINDEXREF_H
+
+#include "blackmisc/blackmiscexport.h"
+#include "blackmisc/typetraits.h"
+#include <QVector>
+
+namespace BlackMisc
+{
+    class CPropertyIndexRef;
+
+    namespace Private
+    {
+        //! \private
+        template <class T, class X>
+        int compareByProperty(const T &a, const T &b, const CPropertyIndexRef &index, std::true_type, X)
+        {
+            return a.comparePropertyByIndex(index, b);
+        }
+        //! \private
+        template <class T>
+        int compareByProperty(const T &a, const T &b, const CPropertyIndexRef &index, std::false_type, std::true_type)
+        {
+            return compare(a.propertyByIndex(index), b.propertyByIndex(index));
+        }
+        //! \private
+        template <class T>
+        int compareByProperty(const T &, const T &, const CPropertyIndexRef &, std::false_type, std::false_type)
+        {
+            qFatal("Not implemented");
+            return 0;
+        }
+    }
+
+    /*!
+     * Non-owning reference to a CPropertyIndex with a subset of its features.
+     */
+    class BLACKMISC_EXPORT CPropertyIndexRef
+    {
+    public:
+        //! Construct from a single index.
+        CPropertyIndexRef(int index);
+
+        //! Construct from the data of a CPropertyIndex.
+        explicit CPropertyIndexRef(const QVector<int> &indexes);
+
+        //! Forbid accidental constructor from an rvalue.
+        explicit CPropertyIndexRef(QVector<int> &&) = delete;
+
+        //! Copy with first element removed
+        CPropertyIndexRef copyFrontRemoved() const;
+
+        //! Is nested index?
+        bool isNested() const;
+
+        //! Myself index, used with nesting
+        bool isMyself() const;
+
+        //! Empty?
+        bool isEmpty() const;
+
+        //! Front to integer
+        int frontToInt() const;
+
+        //! Starts with given index?
+        bool startsWith(int index) const;
+
+        //! \copydoc BlackMisc::Mixin::String::toQString
+        QString toQString(bool i18n = false) const;
+
+        //! First element casted to given type, usually the PropertIndex enum
+        template<class CastType> CastType frontCasted() const
+        {
+            static_assert(std::is_enum<CastType>::value || std::is_integral<CastType>::value, "CastType must be an enum or integer");
+            return static_cast<CastType>(frontToInt());
+        }
+
+        //! Compare with index given by enum
+        template<class EnumType> bool startsWithPropertyIndexEnum(EnumType ev) const
+        {
+            static_assert(std::is_enum<EnumType>::value, "Argument must be an enum");
+            return this->startsWith(static_cast<int>(ev));
+        }
+
+        //! Return a predicate function which can compare two objects based on this index
+        auto comparator() const
+        {
+            return [index = *this](const auto & a, const auto & b)
+            {
+                using T = std::decay_t<decltype(a)>;
+                return Private::compareByProperty(a, b, index, THasComparePropertyByIndex<T>(), THasPropertyByIndex<T>());
+            };
+        }
+
+        //! an empty property index
+        static CPropertyIndexRef empty() { return -1; }
+
+    private:
+        const int *m_begin = nullptr;
+        int m_sizeOrIndex = -1;
+    };
+}
+
+#endif