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88 lines
2.8 KiB
C++
88 lines
2.8 KiB
C++
/* Copyright (C) 2015
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* swift project Community / Contributors
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*
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* This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
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* directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
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* including this file, may be copied, modified, propagated, or distributed except according to the terms
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* contained in the LICENSE file.
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*/
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//! \file
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#ifndef BLACKMISC_INHERITANCE_TRAITS_H
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#define BLACKMISC_INHERITANCE_TRAITS_H
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#include <QMetaType>
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#include <type_traits>
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namespace BlackMisc
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{
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class CEmpty;
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/*!
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* If T has a member typedef base_type, this trait will obtain it, otherwise void.
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*/
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template <class T>
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class BaseOf
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{
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//template <typename U> static typename U::base_type *test(int);
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template <typename U> static typename U::base_type *test(typename std::enable_if<! std::is_same<typename U::base_type, CEmpty>::value, int>::type);
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template <typename U> static void *test(...);
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public:
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//! The declared base_type of T, or void if there is none.
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typedef typename std::remove_pointer<decltype(test<T>(0))>::type type;
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};
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/*!
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* It T has a member typedef base_type which is a registered metatype, this trait will obtain it, otherwise void.
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*/
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template <class T>
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class MetaBaseOf
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{
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public:
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//! Type of T::base_type, or void if not declared.
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typedef typename std::conditional<QMetaTypeId<typename BaseOf<T>::type>::Defined, typename BaseOf<T>::type, void>::type type;
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};
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/*!
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* If T has a member typedef base_type which has a member propertyByIndex, this trait will obtain it, otherwise void.
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*/
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template <class T>
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class IndexBaseOf
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{
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// http://en.wikibooks.org/wiki/More_C++_Idioms/Member_Detector
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struct Empty {};
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struct Fallback { int propertyByIndex; };
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template <int Fallback:: *> struct int_t { typedef int type; };
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template <typename U> struct Derived : public Fallback, public std::conditional<std::is_void<U>::value, Empty, U>::type {};
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template <typename U> static void test(typename int_t<&Derived<U>::propertyByIndex>::type);
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template <typename U> static U test(...);
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public:
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//! Type of T::base_type, or void if not declared.
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typedef decltype(test<typename BaseOf<T>::type>(0)) type;
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};
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/*!
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* Alias for typename BaseOf<T>::type.
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*/
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template <class T>
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using BaseOfT = typename BaseOf<T>::type;
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/*!
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* Alias for typename MetaBaseOf<T>::type.
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*/
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template <class T>
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using MetaBaseOfT = typename MetaBaseOf<T>::type;
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/*!
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* Alias for typename IndexBaseOf<T>::type.
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*/
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template <class T>
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using IndexBaseOfT = typename IndexBaseOf<T>::type;
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}
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#endif
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