From: ts <decoux@...>
Date: 2001-09-25T14:15:45+09:00
Subject: [ruby-talk:21658] Re: C++ / Ruby questions again

>>>>> "B" == =?ISO-8859-1?Q?Bernhard Gl=FCck?= <jglueck@vol.at> writes:

B> Hm that's a nice thing for ruby. but unfortunatly it does not help
B> me... I need to  call a ruby instance method from C++ ... so i need to
B> know in C++ how many parameters the ruby instance method i want to
B> call takes....
B> So the ruby method for doing this does not help me..
B> Is there a way of doing the same using the C API ? 

 Well, when you call :

 rb_funcall(obj, rb_intern("tt"), 1, INT2FIX(12));

 this is like if you have made the method call (in ruby)

   obj.tt(12)

 If I've understood actually you use rb_respond_to(), this mean that you
 write something like this 

   if (rb_respond_to(obj, rb_intern("tt"))) {
      VALUE res = rb_funcall2(obj, rb_intern("tt"), 0, 0); 
   }
   else {
     /* send an error message */
   }

 You can replace it with something like this

   if (rb_respond_to(obj, rb_intern("tt"))) {
      VALUE method, arity;
      method = rb_funcall(obj, rb_intern("method"), 1, rb_str_new2("tt"));
      arity = rb_funcall2(method, rb_intern("arity"), 0, 0);
      rb_warn("tt take %d args", NUM2INT(arity));
   }
   else {
     /* send an error message */
   }



Guy Decoux