如何在精神上解析字符串並將其用作返回值

Question

我需要解析一個鍵值對，其中鍵本身是一個固定字符串 lke 'cmd' 在示例中。 不幸的是 qi::lit 沒有綜合屬性並且 qi::char_ 解析沒有固定的字符串。 以下代碼無法編譯。 執行后我需要那個 result.name == cmd 。

#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <iomanip>
#include <string>

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

struct CommandRuleType
{
  std::string name;
  int arg;
};

BOOST_FUSION_ADAPT_STRUCT(CommandRuleType, name, arg)

int main() {
    qi::rule<std::string::const_iterator, CommandRuleType(), qi::space_type> rule = qi::lit("cmd") >> "=" >> qi::int_;

    for (std::string const s : {"cmd = 1" }) {
        std::cout << std::quoted(s) << " -> ";
        CommandRuleType result;
        if (qi::phrase_parse(s.begin(), s.end(), rule, qi::space, result)) {
            std::cout << "result: " << result.name << "=" << result.arg << "\n";
        } else {
            std::cout << "parse failed\n";
        }
    }
}

Answer 1

qi::lit不公開屬性。 qi::string會：

    rule = qi::string("cmd") >> "=" >> qi::int_;

住在科利魯

#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/qi.hpp>
#include <iomanip>
#include <string>

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

struct CommandRuleType {
    std::string name;
    int arg;
};

BOOST_FUSION_ADAPT_STRUCT(CommandRuleType, name, arg)

int main() {
    qi::rule<std::string::const_iterator, CommandRuleType(), qi::space_type>
        rule = qi::string("cmd") >> "=" >> qi::int_;

    for (std::string const s : { "cmd = 1" }) {
        std::cout << std::quoted(s) << " -> ";
        CommandRuleType result;
        if (qi::phrase_parse(s.begin(), s.end(), rule, qi::space, result)) {
            std::cout << "result: " << result.name << "=" << result.arg << "\n";
        } else {
            std::cout << "parse failed\n";
        }
    }
}

印刷

"cmd = 1" -> result: cmd=1