robot/include/rttr/detail/misc/register_wrapper_mapper_conversion.h

/************************************************************************************
*                                                                                   *
*   Copyright (c) 2014, 2015 - 2017 Axel Menzel <info@rttr.org>                     *
*                                                                                   *
*   This file is part of RTTR (Run Time Type Reflection)                            *
*   License: MIT License                                                            *
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#ifndef RTTR_REGISTER_WRAPPER_MAPPER_CONVERSION_H_
#define RTTR_REGISTER_WRAPPER_MAPPER_CONVERSION_H_

#include "rttr/detail/base/core_prerequisites.h"

#include "rttr/detail/misc/misc_type_traits.h"

#include <type_traits>

namespace rttr
{
template<typename... U> struct type_list;

namespace detail
{

/*!
 * Determine if the given type \a T has a wrapper_mapper method called `convert`.
 */
template <typename T>
class has_conversion_function_impl
{
    typedef char YesType[1];
    typedef char NoType[2];

    template <typename U> static YesType& check(decltype(&wrapper_mapper<U>::convert));
    template <typename U> static NoType&  check(...);
public:
    static RTTR_CONSTEXPR_OR_CONST bool value = (sizeof(check<raw_type_t<T>>(0)) != sizeof(YesType));
};

/*!
 * If \a T has a wrapper_mapper function `convert` then is the same like `std::true_type`, otherwise inherits from `std::false_type`.
 */
template<typename T>
using has_wrapper_conv_func = std::integral_constant<bool, has_conversion_function_impl<T>::value>;

/////////////////////////////////////////////////////////////////////////////////////

/*!
 * Registers for the given type \p DerivedClass a conversion function
 * from \ref wrapper_mapper<T> from and to the types in the list `T...`.
 */
template<typename DerivedClass, typename... T>
struct create_wrapper_conversion;

template<typename DerivedClass>
struct create_wrapper_conversion<DerivedClass>
{
    static RTTR_INLINE void perform() { }
};

template<typename DerivedClass, typename BaseClass, typename... U>
struct create_wrapper_conversion<DerivedClass, BaseClass, U...>
{
    static RTTR_INLINE void perform()
    {
        static_assert(has_base_class_list<BaseClass>::value, "The parent class has no base class list defined - please use the macro RTTR_ENABLE");
        type::register_converter_func(wrapper_mapper<DerivedClass>::template convert<BaseClass>);
        using return_type = typename function_traits<decltype(&wrapper_mapper<DerivedClass>::template convert<BaseClass>)>::return_type;
        // TO DO: remove raw_type_t, std::shared_ptr<const T> should also be converted, when necessary
        using wrapped_derived_t = raw_type_t<wrapper_mapper_t<DerivedClass>>;
        type::register_converter_func(wrapper_mapper<return_type>::template convert<wrapped_derived_t>);

        create_wrapper_conversion<DerivedClass, typename BaseClass::base_class_list>::perform();
        // continue with the rest
        create_wrapper_conversion<DerivedClass, U...>::perform();
    }
};

template<typename DerivedClass, class... BaseClassList>
struct create_wrapper_conversion<DerivedClass, type_list<BaseClassList...>> : create_wrapper_conversion<DerivedClass, BaseClassList...> { };

/////////////////////////////////////////////////////////////////////////////////////

template<typename T, typename Enable = void>
struct reg_wrapper_converter_for_base_classes
{
    reg_wrapper_converter_for_base_classes()
    {
    }
};

template<typename T>
struct reg_wrapper_converter_for_base_classes<T, typename std::enable_if<is_wrapper<T>::value && has_base_class_list<raw_type_t<wrapper_mapper_t<T>>>::value>::type>
{
    reg_wrapper_converter_for_base_classes()
    {
        create_wrapper_conversion<T, typename raw_type_t<wrapper_mapper_t<T>>::base_class_list>::perform();
    }
};

/////////////////////////////////////////////////////////////////////////////////////

}   // end namespace detail
}   // end namespace rttr

#endif // RTTR_REGISTER_WRAPPER_MAPPER_CONVERSION_H_