staj_object_iterator.md

jsoncons::staj_object_iterator

template <class T>
using staj_object_iterator = basic_staj_object_iterator<char,T>;

Header

#include <jsoncons/staj_iterator.hpp>

A staj_object_iterator is an InputIterator that accesses the individual stream events from a staj_reader and, provided that when it is constructed the current stream event has type begin_object, it returns the elements of the JSON object as items of type std::pair<string_type,T>. If when it is constructed the current stream event does not have type begin_object, it becomes equal to the default-constructed iterator.

Member types

Member type	Definition
char_type	char
key_type	std::basic_string<char_type>
value_type	std::pair<string_type,T>
difference_type	std::ptrdiff_t
pointer	value_type*
reference	value_type&
iterator_category	std::input_iterator_tag

Constructors

staj_object_iterator() noexcept; // (1)

staj_object_iterator(basic_staj_reader<char_type>& reader); // (2)

staj_object_iterator(basic_staj_reader<char_type>& reader,
                     std::error_code& ec);  // (3)

(1) Constructs the end iterator

(2) Constructs a staj_object_iterator that refers to the first member of the object following the current stream event begin_object. If there is no such member, returns the end iterator. If a parsing error is encountered, throws a parse_error.

(3) Constructs a staj_object_iterator that refers to the first member of the object following the current stream event begin_object. If there is no such member, returns the end iterator. If a parsing error is encountered, returns the end iterator and sets ec.

Member functions

const key_value_type& operator*() const

const key_value_type* operator->() const

staj_object_iterator& operator++();
staj_object_iterator operator++(int); 
staj_object_iterator& increment(std::error_code& ec);

Advances the iterator to the next object member.

Non-member functions

template <class T>
bool operator==(const staj_object_iterator<T>& a, const staj_object_iterator<T>& b)

template <class T>
bool operator!=(const staj_object_iterator<T>& a, const staj_object_iterator<T>& b)

template <class T>
staj_object_iterator<T> begin(staj_object_iterator<T> iter) noexcept; // (1)

template <class T>
staj_object_iterator<T> end(const staj_object_iterator<T>&) noexcept; // (2)

(1) Returns iter unchanged

(2) Returns a default-constructed stax_array_iterator, which serves as an end iterator. The argument is ignored.

The begin and end non-member functions enable the use of stax_array_iterators with range-based for loops.

Examples

Iterate over a JSON object, returning key-json value pairs

const std::string example = R"(
{
   "application": "hiking",
   "reputons": [
   {
       "rater": "HikingAsylum.array_example.com",
       "assertion": "is-good",
       "rated": "sk",
       "rating": 0.90
     }
   ]
}
)";

int main()
{
    std::istringstream is(object_example);

    json_staj_reader reader(is);

    staj_object_iterator<json> it(reader);

    for (const auto& kv : it)
    {
        std::cout << kv.first << ":\n" << pretty_print(kv.second) << "\n";
    }
    std::cout << "\n\n";
}

Output:

application:
"hiking"
reputons:
[
    {
        "assertion": "is-good",
        "rated": "sk",
        "rater": "HikingAsylum.array_example.com",
        "rating": 0.90
    }
]