Re: One question about table driven and function pointer

you could eventually do it the following way :

     #include <map>
     #include <iostream>

     template< typename Arg >
         class command_list
         {
         public:
             void register_command( char const *name, void (*cb)
( Arg ) )
             { command_map[name] = cb; }

             void call( char const *name, Arg arg )
             { command_map[name](arg); }

         private:
             std::map<std::string, void (*)( Arg )> command_map;
         };

     class commands
         : public command_list<std::string>
         , public command_list<int>
     {
     public:
         template< typename Arg >
             void register_command( char const *name, void (*cb)
( Arg ) )
             { static_cast<command_list<Arg> &>(*this).register_command
(name, cb); }

         template< typename Arg >
             void operator()( char const *name, Arg arg )
             { static_cast<command_list<Arg> &>(*this).call(name,
arg); }
     };

     void north( int i ) { std::cerr << "in north( int i = " << i << " )
\n"; }
     void south( std::string s ) { std::cerr << "in south( std::string
const &s = '" << s << "' )\n"; }
     void east( std::string s ) { std::cerr << "in east( std::string
const &s = '" << s << "' )\n"; }
     void west( int i ) { std::cerr << "in west( int i = " << i << " )
\n"; }

     int main( )
     {
         commands cmds;

         cmds.register_command("north", &north);
         cmds.register_command("south", &south);
         cmds.register_command("east", &east);
         cmds.register_command("west", &west);

         cmds("north", 0);
         cmds("south", std::string("hello"));
         cmds("east", std::string("again"));
         cmds("west", 1);
     }

This is a very simple implementation, and there are several points
you'll want to address :
- You most probably want to check for invalid names and duplicate
registered functions.
- Argument passing is not perfect as everything is passed by copy.
That can be fixed with a little template magic.
- You can't rely on implicit conversions to call commands.
- Changes can be made to the internals of 'command_list' to use a
static map.

--
Olivier

      [ See http://www.gotw.ca/resources/clcm.htm for info about ]
      [ comp.lang.c++.moderated. First time posters: Do this! ]