From: Mohit Sindhwani <mo_mail@...>
Date: 2008-12-26T14:40:55+09:00
Subject: Re: Calling Ruby from Delphi

Rob Ram wrote:
> I want to call an embedded ruby function from Delphi 2009. A C or C++
> example is also ok.  For example on the Ruby side:
>
>  def myFunction(a,b,c)
>    rv1=a*b -c
>    rv2=a**2 + b**2
>    rv3=b*c
>    return rv1, rv2, rv3
>   end
>
>  The above function is just some non-sense, but hopefully easy to use as
> an example. MyExample.rb contains the above script.
>
> On the Delphi side:
>
> Starting with:
>
> fState := 0;
> ruby_init;
> ruby_init_loadpath;
> rb_set_safe_level(0);
> ruby_script('embedded'); // or should it be ruby_script(‘ruby’)
>
>
> Ok now I have no clue as to what top do next. Somehow MyExample.rb must
> be loaded.
>
> Maybe:
> rb_load_file(‘MyExample.rb’) ???
>
> Next call myFunction(a,b,c) ???
>
> I found rb_funcall2 and VALUE is defined as:  typedef unsigned long
> VALUE
> However I do not have documentation that explains the meaning of recv or
> how to get the parameter for recv.
>
>
>
> VALUE rb_funcall2(VALUE recv,
>     ID   mid,
>     int   argc,
>     const VALUE *   argv
>            )
>
>
> Any help or suggestions are appreciated.
>   
Hi Rob,

This is some of the stuff that I use in a Borland C++ Builder 
application - not sure if it helps you.  The sequence is exaqctly the 
same as what the online version of PickAxe recommends, if I remember 
correctly.

/* Initialize the Ruby VM */
void rubyVM_initialize()
{
    ruby_init();
    ruby_init_loadpath();
    ruby_script("embedded");  //set a name that the script will use
    return;
}

/* Finalize the Ruby VM */
void rubyVM_finalize()
{
    ruby_finalize();
}

/* Functions to call the functions in Ruby script */
static VALUE wrap_sum(VALUE args) {
  VALUE *values = (VALUE *)args;
  VALUE summer = values[0];
  VALUE max = values[1];
                   //object, function, count?, argument
  return rb_funcall(summer, id_sum, 1, max);
}

static VALUE protected_sum(VALUE summer, VALUE max) {
  int error;
  VALUE args[2];
  VALUE result;
  args[0] = summer;
  args[1] = max;
  result = rb_protect(wrap_sum, (VALUE)args, &error);
  return error ? Qnil : result;
}

/* Sample script execution */
int run_a_script(void)
{
  int value;
  int *next = Values;
  char output[200];

  /* Call ruby VM init first */
  rubyVM_initialize();
  rb_require ("sum.rb");  //script that you want to use

  /* Instantiate the class (Summer) you want to use */
  VALUE summer = rb_class_new_instance(0, 0,
          rb_const_get(rb_cObject, rb_intern("Summer")));

  /* Access the function in that class */
  /* Note id_sum is a global variable below */
  id_sum = rb_intern("sum");  //the function

  while (value = *next++) {
    /* The next line does the hard work through 2 functions */
    VALUE result = protected_sum(summer, INT2NUM(value));
    if (NIL_P(result))
    {
      sprintf(output,"Sum to %d doesn't compute!\n", value);
    }
    else
    {
      sprintf(output,"Sum to %d is %d\n", value, NUM2INT(result));
    }
    //MessageBox(NULL,output,"Ruby result!",MB_OK);

  }

  //rubyVM_finalize();
  //return;
}

I'm sorry I'm in a bit of a rush, but do ask again - I'll reply with 
more details if this doesn't help.  Essentially, I think what you need is:
*   rb_require ("sum.rb");  //script that you want to use
*   VALUE result = protected_sum(summer, INT2NUM(value));
*   See the wrapped functions to pack the parameters and safely call the 
function
*   rb_funcall(summer, id_sum, 1, max); // I think this is object, 
function_number, # of parameters, max

Hopefully this will help: 
http://whytheluckystiff.net/ruby/pickaxe/html/ext_ruby.html

Cheers
Mohit.