Class iteration_proxy_value

native/thirdpart/json/json.hpp:3297–3382

    target = std::to_string(value);
}
template <typename IteratorType> class iteration_proxy_value
{
  public:
    using difference_type = std::ptrdiff_t;
    using value_type = iteration_proxy_value;
    using pointer = value_type * ;
    using reference = value_type & ;
    using iterator_category = std::input_iterator_tag;
    using string_type = typename std::remove_cv< typename std::remove_reference<decltype( std::declval<IteratorType>().key() ) >::type >::type;

  private:
    /// the iterator
    IteratorType anchor;
    /// an index for arrays (used to create key names)
    std::size_t array_index = 0;
    /// last stringified array index
    mutable std::size_t array_index_last = 0;
    /// a string representation of the array index
    mutable string_type array_index_str = "0";
    /// an empty string (to return a reference for primitive values)
    const string_type empty_str = "";

  public:
    explicit iteration_proxy_value(IteratorType it) noexcept : anchor(it) {}

    /// dereference operator (needed for range-based for)
    iteration_proxy_value& operator*()
    {
        return *this;
    }

    /// increment operator (needed for range-based for)
    iteration_proxy_value& operator++()
    {
        ++anchor;
        ++array_index;

        return *this;
    }

    /// equality operator (needed for InputIterator)
    bool operator==(const iteration_proxy_value& o) const
    {
        return anchor == o.anchor;
    }

    /// inequality operator (needed for range-based for)
    bool operator!=(const iteration_proxy_value& o) const
    {
        return anchor != o.anchor;
    }

    /// return key of the iterator
    const string_type& key() const
    {
        assert(anchor.m_object != nullptr);

        switch (anchor.m_object->type())