Spirit.X3 : using push_back_container traits with list parser - boost

Question

I have a class having public ctor and some add() method:
class object
{
object() {}
template <typename>
void add(T&& val) { // some adding here}
}
The main question I'm faced is how can I adopt spirit.x3 list parser to use object::add() method instead of std::vector<>::push_back ?
I was easily able to achieve what I need with simple
x3::int_ % ','
parser (live demo) using the following code :
#include <boost/spirit/home/x3.hpp>
#include <iostream>
#include <vector>
namespace x3 = boost::spirit::x3;
namespace parse_to_object
{
struct object
{
using value_type = int;
object() { std::cout << "object::object() - invoked" << std::endl; }
void add(value_type val) { _data.push_back(val); }
std::vector<value_type> _data;
};
const x3::rule<struct Test, object> r_ints("r_ints");
const auto r_ints_def = x3::int_ % ',';
BOOST_SPIRIT_DEFINE(r_ints);
}
namespace boost { namespace spirit { namespace x3 { namespace traits {
template<>
struct push_back_container<parse_to_object::object>
{
template<typename T>
static bool call(parse_to_object::object& obj, T&& val)
{
obj.add(std::move(val));
return true;
}
};
}}}}
int main()
{
const std::string text("1,2,3,4");
auto begin = std::begin(text);
const auto end = std::end(text);
parse_to_object::object result;
const auto ok = x3::phrase_parse(begin, end, parse_to_object::r_ints, x3::space, result);
std::cout << "ok = " << std::boolalpha << (ok && begin == end) << std::endl;
std::copy(result._data.begin(), result._data.end(), std::ostream_iterator<int>(std::cout, " "));
return 0;
}
But unfortunately, when I tried more compilcated example like
'{' >> x3::int_ >> ':' >> x3::int_ >> '}') % ','
I'm getting the compilation error (live demo) :
/opt/wandbox/boost-1.67.0/clang-head/include/boost/spirit/home/x3/support/traits/container_traits.hpp:102:45: error: no type named 'iterator' in 'parse_to_object::object'
: mpl::identity {};
Could somebody assist with spirit.x3 traits and give some example how to abopt custom class to be used instead of std::vector<> for list parser ?

Answer 1

In the end it's down to a missing include:
#include <boost/fusion/adapted/std_pair.hpp>
std::pair isn't adapted by default.
Side note: std::move should be std::forward<T> with "universal references" (or perfect forwarding)
Live On Coliru
#define BOOST_SPIRIT_X3_DEBUG
#include <boost/fusion/adapted/std_pair.hpp>
#include <boost/spirit/home/x3.hpp>
#include <iostream>
#include <vector>
namespace x3 = boost::spirit::x3;
namespace parse_to_object
{
struct object
{
using value_type = std::pair<int,int>;
object() { std::cout << "object::object() - invoked" << std::endl; }
void add(value_type val) { _data.push_back(std::move(val)); }
std::vector<std::pair<int,int>> _data;
};
const x3::rule<struct Test, object> r_ints("r_ints");
const auto r_ints_def = ('{' >> x3::int_ >> ':' >> x3::int_ >> '}') % ',';
BOOST_SPIRIT_DEFINE(r_ints)
}
namespace boost { namespace spirit { namespace x3 { namespace traits {
template<> struct push_back_container<parse_to_object::object>
{
template<typename T>
static bool call(parse_to_object::object& obj, T&& val)
{
obj.add(std::forward<T>(val));
return true;
}
};
}}}}
int main()
{
const std::string text("{1:2},{3:4}");
auto begin = std::begin(text), end = std::end(text);
parse_to_object::object result;
auto ok = phrase_parse(begin, end, parse_to_object::r_ints >> x3::eoi, x3::space, result);
std::cout << "ok = " << std::boolalpha << ok << "\n";
for (auto& p : result._data)
std::cout << "{" << p.first << ", " << p.second << "} ";
std::cout << "\n";
}
Prints
object::object() - invoked
<r_ints>
<try>{1:2},{3:4}</try>
<success></success>
<attributes></attributes>
</r_ints>
ok = true
{1, 2} {3, 4}