staj_array_iterator.md

jsoncons::staj_array_iterator

#include <jsoncons/staj_iterator.hpp>

template<
    class T,
    class Json
    >
class staj_array_iterator

A staj_array_iterator is an InputIterator that accesses the individual stream events from a staj_cursor and, provided that when it is constructed the current stream event has type staj_event_type::begin_array, it retrieves the elements of the JSON array as items of type T. If when it is constructed the current stream event does not have type staj_event_type::begin_array, it becomes equal to the default-constructed iterator.

Member types

Member type	Definition
char_type	Json::char_type
value_type	T
difference_type	std::ptrdiff_t
pointer	value_type*
reference	value_type&
iterator_category	std::input_iterator_tag

Constructors

staj_array_iterator() noexcept; (1)

staj_array_iterator(staj_array_view<T, Json>& view); (2)

staj_array_iterator(staj_array_view<T, Json>& view,
                    std::error_code& ec); (3)

(1) Constructs the end iterator

(2) Constructs a staj_array_iterator that refers to the first element of the array following the current stream event begin_array. If there is no such element, returns the end iterator. If a parsing error is encountered, throws a ser_error.

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

Member functions

const T& operator*() const

const T* operator->() const

staj_array_iterator& operator++()
staj_array_iterator& increment(std::error_code& ec)
staj_array_iterator operator++(int) 

Advances the iterator to the next array element.

Non-member functions

template <class class T, class Json>
bool operator==(const staj_array_iterator<T, Json>& a, const staj_array_iterator<T, Json>& b);

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

Examples

Iterate over a JSON array, returning json values

const std::string example = R"(
[ 
  { 
      "employeeNo" : "101",
      "name" : "Tommy Cochrane",
      "title" : "Supervisor"
  },
  { 
      "employeeNo" : "102",
      "name" : "Bill Skeleton",
      "title" : "Line manager"
  }
]
)";

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

    json_stream_cursor cursor(is);

    auto view = staj_array<json>(cursor);

    for (const auto& j : view)
    {
        std::cout << pretty_print(j) << "\n";
    }
    std::cout << "\n\n";
}

Output:

{
    "employeeNo": "101",
    "name": "Tommy Cochrane",
    "title": "Supervisor"
}
{
    "employeeNo": "102",
    "name": "Bill Skeleton",
    "title": "Line manager"
}

Iterate over the JSON array, returning employee values

namespace ns {

    struct employee
    {
        std::string employeeNo;
        std::string name;
        std::string title;
    };

} // namespace ns

JSONCONS_ALL_MEMBER_TRAITS(ns::employee, employeeNo, name, title)
      
int main()
{
    std::istringstream is(example);

    json_stream_cursor cursor(is);

    auto view = staj_array<ns::employee>(cursor);

    for (const auto& val : view)
    {
        std::cout << val.employeeNo << ", " << val.name << ", " << val.title << "\n";
    }
    std::cout << "\n\n";
}

Output:

101, Tommy Cochrane, Supervisor
102, Bill Skeleton, Line manager