Can Boost Program_options separate comma separated argument values

问题

If my command line is:

> prog --mylist=a,b,c

Can Boost's program_options be setup to see three distinct argument values for the mylist argument? I have configured program_options as:

namespace po = boost::program_options;
po::options_description opts("blah")

opts.add_options()
    ("mylist", std::vector<std::string>>()->multitoken, "description");

po::variables_map vm;
po::store(po::parse_command_line(argc, argv, opts), vm);
po::notify(vm);

When I check the value of the mylist argument, I see one value as a,b,c. I'd like to see three distinct values, split on comma. This works fine if I specify the command line as:

> prog --mylist=a b c

or

> prog --mylist=a --mylist=b --mylist=c

Is there a way to configure program_options so that it sees a,b,c as three values that should each be inserted into the vector, rather than one?

I am using boost 1.41, g++ 4.5.0 20100520, and have enabled c++0x experimental extensions.

EDIT:

The accepted solution works but ends up being more complicated, IMO, than just iterating through a vector and splitting the values manually. In the end, I took the suggestion from James McNellis and implemented it that way. His solution wasn't submitted as an answer, however, so I accepted the other correct solution from hkaiser. Both worked, but the manual tokenization is clearer.

回答1:

You could register a custom validator for your option:

namespace po = boost::program_options;

struct mylist_option 
{
    // values specified with --mylist will be stored here
    vector<std::string> values;

    // Function which validates additional tokens from command line.
    static void
    validate(boost::any &v, std::vector<std::string> const &tokens)
    {
        if (v.empty())
            v = boost::any(mylist_option());

        mylist_option *p = boost::any_cast<mylist_option>(&v);
        BOOST_ASSERT(p);

        boost::char_separator<char> sep(",");
        BOOST_FOREACH(std::string const& t, tokens)
        {
            if (t.find(",")) {
                // tokenize values and push them back onto p->values
                boost::tokenizer<boost::char_separator<char> > tok(t, sep);
                std::copy(tok.begin(), tok.end(), 
                    std::back_inserter(p->values));
            }
            else {
                // store value as is
                p->values.push_back(t);
            }
        }
    }
};

which then can be used as:

opts.add_options()                 
    ("mylist", po::value<mylist_option>()->multitoken(), "description");

and:

if (vm.count("mylist"))
{
    // vm["mylist"].as<mylist_option>().values will hold the value specified
    // using --mylist
}

回答2:

I haven't tried doing so myself, but you could possibly be able to use the same approach as in custom_syntax.cpp example that's provided with program_options, to write your own parser that you can provide as an extra parser. There's a bit of info here with a short example. Then you could either combine that with James' suggestion of using boost::tokenizer, or just follow his suggestion.

回答3:

here is what I am using right now:

template<typename T, int N> class mytype;
template<typename T, int N> std::istream& operator>> (std::istream& is, mytype<T,N>& rhs);
template<typename T, int N> std::ostream& operator<< (std::ostream& os, const mytype<T,N>& rhs);
template < typename T, int N >
struct mytype
{
  T values[N];
  friend std::istream& operator>> <>(std::istream &is, mytype<T,N> &val);
  friend std::ostream& operator<< <>(std::ostream &os, const mytype<T,N> &val);
};
template<typename T, int N>
inline std::istream& operator>>(std::istream &is, mytype<T,N> &val)
{
  for( int i = 0; i < N; ++i )
    {
    if( i )
      if (is.peek() == ',')
        is.ignore();
    is >> val.values[i];
    }
  return is;
}
template<typename T, int N>
inline std::ostream& operator<<(std::ostream &os, const mytype<T,N> &val)
{
  for( int i = 0; i < N; ++i )
    {
    if( i ) os << ',';
    os << val.values[i];
    }
  return os;
}

int main(int argc, char *argv[])
{
  namespace po = boost::program_options;

  typedef mytype<int,2> mytype; // let's test with 2 int
  mytype my;
  try
    {
    po::options_description desc("the desc");
    desc.add_options()
      ("mylist", po::value< mytype >(&my), "mylist desc")
      ;

    po::variables_map vm;
    po::store(po::command_line_parser(argc, argv).options(desc).run(), vm);
    po::notify(vm);

    if (vm.count("mylist"))
      {
      const mytype ret = vm["mylist"].as<mytype >();
      std::cerr << "mylist: " << ret << " or: " << my << std::endl;
      }
    }
  catch(std::exception& e)
    {
    std::cout << e.what() << "\n";
    }    
  return 0;
}

来源：https://stackoverflow.com/questions/3065109/can-boost-program-options-separate-comma-separated-argument-values