该指令返回一个fusion::vector2<>，其中主题的属性作为其第一个成员，与合成属性对应的字符串作为其第二个成员。我认为这是最简单的重用方法，只要您充分调整结构即可。我不确定fusion::vector2<> 是否是处理属性的最佳方式，但在我所做的有限测试中，它运行良好。使用此指令，ints_string 规则将是：
ints_string=custom::annotate[ints];
//or ints_string=custom::annotate[qi::lexeme[qi::int_ % qi::char_(",_")]];
Example on LWS.
annotate.hpp
#if !defined(ANNOTATE_HPP)
#define ANNOTATE_HPP
#if defined(_MSC_VER)
#pragma once
#endif
#include <boost/spirit/home/qi/meta_compiler.hpp>
#include <boost/spirit/home/qi/skip_over.hpp>
#include <boost/spirit/home/qi/parser.hpp>
#include <boost/spirit/home/support/unused.hpp>
#include <boost/spirit/home/support/common_terminals.hpp>
#include <boost/spirit/home/qi/detail/attributes.hpp>
#include <boost/spirit/home/support/info.hpp>
#include <boost/spirit/home/support/handles_container.hpp>
namespace custom
{
BOOST_SPIRIT_TERMINAL(annotate);
}
namespace boost { namespace spirit
{
///////////////////////////////////////////////////////////////////////////
// Enablers
///////////////////////////////////////////////////////////////////////////
template <>
struct use_directive<qi::domain, custom::tag::annotate> // enables annotate
: mpl::true_ {};
}}
namespace custom
{
template <typename Subject>
struct annotate_directive : boost::spirit::qi::unary_parser<annotate_directive<Subject> >
{
typedef Subject subject_type;
annotate_directive(Subject const& subject)
: subject(subject) {}
template <typename Context, typename Iterator>
struct attribute
{
typedef
boost::fusion::vector2<
typename boost::spirit::traits::attribute_of<subject_type, Context, Iterator>::type
,std::string
>
type;
};
template <typename Iterator, typename Context
, typename Skipper, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, Context& context, Skipper const& skipper
, Attribute& attr) const
{
boost::spirit::qi::skip_over(first, last, skipper);
Iterator save = first;
typename boost::spirit::traits::attribute_of<subject_type, Context, Iterator>::type attr_;
if(subject.parse(first, last, context, skipper, attr_))
{
boost::spirit::traits::assign_to(attr_,boost::fusion::at_c<0>(attr));
boost::spirit::traits::assign_to(std::string(save,first),boost::fusion::at_c<1>(attr));
return true;
}
first = save;
return false;
}
template <typename Context>
boost::spirit::info what(Context& context) const
{
return info("annotate", subject.what(context));
}
Subject subject;
};
}//custom
///////////////////////////////////////////////////////////////////////////
// Parser generators: make_xxx function (objects)
///////////////////////////////////////////////////////////////////////////
namespace boost { namespace spirit { namespace qi
{
template <typename Subject, typename Modifiers>
struct make_directive<custom::tag::annotate, Subject, Modifiers>
{
typedef custom::annotate_directive<Subject> result_type;
result_type operator()(unused_type, Subject const& subject, unused_type) const
{
return result_type(subject);
}
};
}}}
namespace boost { namespace spirit { namespace traits
{
///////////////////////////////////////////////////////////////////////////
template <typename Subject>
struct has_semantic_action<custom::annotate_directive<Subject> >
: unary_has_semantic_action<Subject> {};
///////////////////////////////////////////////////////////////////////////
template <typename Subject, typename Attribute, typename Context
, typename Iterator>
struct handles_container<custom::annotate_directive<Subject>, Attribute
, Context, Iterator>
: unary_handles_container<Subject, Attribute, Context, Iterator> {};
}}}
#endif
main.cpp
#include <iostream>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include "annotate.hpp"
namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
struct ints_type
{
std::vector<int> data;
std::string inttext;
};
struct A
{
std::string header;
ints_type ints;
};
BOOST_FUSION_ADAPT_STRUCT(
ints_type,
(std::vector<int>, data)
(std::string, inttext)
)
BOOST_FUSION_ADAPT_STRUCT(
A,
(std::string, header)
(ints_type, ints)
)
template <typename Iterator>
struct parser : qi::grammar< Iterator, A() >
{
parser() : parser::base_type(start)
{
header %= qi::lexeme[ +qi::alpha ];
ints = qi::lexeme[qi::int_ % qi::char_(",_")];
ints_string = custom::annotate[ints];
start %= header >> ' ' >> ints_string;
}
qi::rule<Iterator, std::string()> header;
qi::rule<Iterator, std::vector<int>() > ints;
qi::rule<Iterator, ints_type() > ints_string;
qi::rule<Iterator, A()> start;
};
int main()
{
A output;
std::string input("out 1,2_3");
auto iter = input.begin();
parser<decltype(iter)> p;
std::string annotation;
bool r = qi::parse(iter, input.end(), custom::annotate[p], output, annotation);
if( !r || iter != input.end() )
{
std::cout << "did not parse";
}
else
{
// would like output.inttext to be "1,2_3"
std::cout << "annotation: " << annotation << std::endl;
std::cout << output.header << ": " << output.ints.inttext << " -> [ ";
for( auto & i: output.ints.data )
std::cout << i << ' ';
std::cout << ']' << std::endl;
}
}