Class iteration_proxy_value

extern/json/json.hpp:5118–5236

    target = 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)
    string_type empty_str{};

  public:
    explicit iteration_proxy_value() = default;
    explicit iteration_proxy_value(IteratorType it, std::size_t array_index_ = 0)
    noexcept(std::is_nothrow_move_constructible<IteratorType>::value
             && std::is_nothrow_default_constructible<string_type>::value)
        : anchor(std::move(it))
        , array_index(array_index_)
    {}

    iteration_proxy_value(iteration_proxy_value const&) = default;
    iteration_proxy_value& operator=(iteration_proxy_value const&) = default;
    // older GCCs are a bit fussy and require explicit noexcept specifiers on defaulted functions
    iteration_proxy_value(iteration_proxy_value&&)
    noexcept(std::is_nothrow_move_constructible<IteratorType>::value
             && std::is_nothrow_move_constructible<string_type>::value) = default;
    iteration_proxy_value& operator=(iteration_proxy_value&&)
    noexcept(std::is_nothrow_move_assignable<IteratorType>::value
             && std::is_nothrow_move_assignable<string_type>::value) = default;
    ~iteration_proxy_value() = default;

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

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

        return *this;
    }

    iteration_proxy_value operator++(int)& // NOLINT(cert-dcl21-cpp)