first.hpp

//                  ReactivePlusPlus library
//
//          Copyright Aleksey Loginov 2022 - present.
//                            TC Wang 2022 - present.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/victimsnino/ReactivePlusPlus
//
 
#pragma once
 
#include <rpp/observables/details/member_overload.hpp>
 
namespace rpp::details
{
struct first_tag;
}
 
namespace rpp::details
{
 
template<constraint::decayed_type Type>
struct first_impl;
 
template<constraint::decayed_type Type, typename SpecificObservable>
struct member_overload<Type, SpecificObservable, first_tag>
{
    auto first() const & requires is_header_included<first_tag, Type>
    {
        return cast_this()->template lift<Type>(first_impl<Type>{});
    }
 
    auto first() && requires is_header_included<first_tag, Type>
    {
        return move_this().template lift<Type>(first_impl<Type>{});
    }
 
private:
    const SpecificObservable* cast_this() const
    {
        return static_cast<const SpecificObservable*>(this);
    }
 
    SpecificObservable&& move_this()
    {
        return std::move(*static_cast<SpecificObservable*>(this));
    }
};
} // namespace rpp::details