nlohmannjson/include/nlohmann/detail/json_ref.hpp

#pragma once

#include <initializer_list>
#include <utility>

#include <nlohmann/detail/meta/type_traits.hpp>

namespace nlohmann
{
namespace detail
{
template<typename BasicJsonType>
class json_ref
{
  public:
    using value_type = BasicJsonType;

    json_ref(value_type&& value)
        : owned_value(std::move(value))
        , value_ref(&owned_value)
        , is_rvalue(true)
    {}

    json_ref(const value_type& value)
        : value_ref(const_cast<value_type*>(&value))
        , is_rvalue(false)
    {}

    json_ref(std::initializer_list<json_ref> init)
        : owned_value(init)
        , value_ref(&owned_value)
        , is_rvalue(true)
    {}

    template <
        class... Args,
        enable_if_t<std::is_constructible<value_type, Args...>::value, int> = 0 >
    json_ref(Args && ... args)
        : owned_value(std::forward<Args>(args)...)
        , value_ref(&owned_value)
        , is_rvalue(true)
    {}

    // class should be movable only
    json_ref(json_ref&&) = default;
    json_ref(const json_ref&) = delete;
    json_ref& operator=(const json_ref&) = delete;
    json_ref& operator=(json_ref&&) = delete;
    ~json_ref() = default;

    value_type moved_or_copied() const
    {
        if (is_rvalue)
        {
            return std::move(*value_ref);
        }
        return *value_ref;
    }

    value_type const& operator*() const
    {
        return *static_cast<value_type const*>(value_ref);
    }

    value_type const* operator->() const
    {
        return static_cast<value_type const*>(value_ref);
    }

  private:
    mutable value_type owned_value = nullptr;
    value_type* value_ref = nullptr;
    const bool is_rvalue = true;
};
}  // namespace detail
}  // namespace nlohmann