[Boost-users] design question for boost::program_options and dynamic options

From: boost_at_[hidden]
Date: 2005-10-31 15:08:38

Hello,

I'm new to the boost::program_options library and tried to use it for a
command pattern based software. The program is launched with the
following commandline:

> program command [Options] <Files>

The program can use different output formatters with
--formatter={XML|binary|text}. Every command and formatter specify their
own set of options.

I first tried to collect all options form the commands and formatters
and parse the command line only once. This lead to the problem, that due
to the different positional options information the commandline parser
always threw an exception due to wrong command line formatting.

Since I couldn't find a way to add mutliple optional option groups to
the parser, I moved the parsing code into my command base class and
query the derived commands for the different required information, like:

class Command
{
  public:
   vritual options_description GetOptionsDescription ();
   virtual options_description GetHiddenOptionsDescription ();
   virtual positional_program_options GetPositionalProgramOptions ();

   virtual Run (variables_map const & vm) = 0;
   int Execute (std::vector<std:.string> args)
   {
    options_description desc;
    descr.add (GetOptionsDescription ()).add (GetHiddenOptionsDescription
());

    variables_map vm;
    store(command_line_parser(args)
        .options(desc).
        .positional(GetPositionalProgramOptions ())
        .run(), vm);
    notify(vm);

    Run (vm);
   }

}

The execute function is called form the program main after the "command"
has been stripped from the commandline and the concrete command was
created by the factory.
So far so good. This works for the different commands, but not for the
formatters.

How can I parse the command line dynamically? E.g. if I encounter the
"--formatter=xml" argument, a new XMLFormatter is created and the
options description from this formatter are added to list of valid options?

I know, that there is the notify mechanism, but this only works after
the commandline has been successfully parsed. And also the custom
parsers do not solve my problem.

Any idea how to solve this issue?

Best regards
Dirk