[Boost-users] [spirit/qi] Error handler not called

26 Jan 2013

      Hi,

I am trying to develop a JSON parser using spirit/qi so far it is not
going bad but I am having serious problem with on_error and error
handler. This is my code:

namespace qi = boost::spirit::qi;
  namespace ascii = boost::spirit::ascii;
  namespace phoenix = boost::phoenix;

  template <typename Iterator>
  struct error_handler
  {
    template <typename, typename, typename, typename>
    struct result
    {
      typedef void type;
    };

    void operator()(Iterator first, Iterator last, Iterator err_pos,
const boost::spirit::info& info) const
    {
      std::cout << "never called";
    }
  };

  template <class Iterator>
  struct JsonGrammar : public qi::grammar<Iterator, Value(), ascii::space_type>
  {
    JsonGrammar() : JsonGrammar::base_type(json, "json"),
error(error_handler<Iterator>())
    {
      using qi::double_;
      using qi::lexeme;
      using qi::char_;
      using qi::int_;
      using qi::on_error;
      using qi::fail;
      using phoenix::construct;
      using phoenix::val;
      using namespace qi::labels;

      qi::on_error<qi::fail>(json, error(_1, _2, _3, _4));

      string %= lexeme['"' >> +(char_ - '"') >> '"'];
      number  = int_;
      member  = string >> ':' >> value;
      array   = '[' >> value % ',' >> ']';
      object  = '{' >> member >> *(',' >> member) >> '}';
      value   = array | object | number | string | qi::bool_ | "null";
      json    = array | object;

      json.name("json");

    }

    phoenix::function<error_handler<Iterator> > const error;
    qi::rule<Iterator, std::string(), ascii::space_type> string;
    qi::rule<Iterator, int(), ascii::space_type> number;
    qi::rule<Iterator, Value(), ascii::space_type> json;
    qi::rule<Iterator, Array(), ascii::space_type> array;
    qi::rule<Iterator, Value(), ascii::space_type> value;
    qi::rule<Iterator, Object(), ascii::space_type> object;
    qi::rule<Iterator, std::pair<std::string, Value>(),
ascii::space_type> member;
  };

now when i try to parse

std::string json = "[1, 2, 3, 4, t]";

parising result is false. but error handelr is never called. What am I
doing wrong?

Regards,
Simon

-- 
Szymon Gatner
The Lordz Games Studio
www.thelordzgamesstudio.com