From: Jan Dvorak <jan.dvorak@...>
Date: 2008-05-06T01:38:16+09:00
Subject: Re: Need more help with Ruby and C

On Monday 05 May 2008 15:44:03 Bryan Richardson wrote:
> Hi Jan,
>
> Alright, that makes sense, thanks for the information.  However, that
> doesn't help me to understand how I can pass a Ruby array of objects to the
> execute method.  Am I missing something here?  Can you help me with this?
>
The array is just an object (everything in ruby is object) which you can 
manipulate from C with rb_ary_* functions.  You wrote the code yourself:

  VALUE foo = rb_ary_entry(foos, 0); // this will return the first element of 
the array

now, rb_* functions operate on (and returns) ruby objects (VALUE), if you want 
to direclty use POD data types in C, you have to convert them, e.g. :

  VALUE val = rb_iv_get(foo,"@value");
  printf("Foo Value: %i\n", NUM2INT(val));

or alternatively 

  printf("Foo Value: %i\n", NUM2INT(rb_iv_get(foo, "@value"));

For integral types there are general macros INT2NUM (c to ruby) and NUM2INT 
(ruby to C), and their variants (FIX2INT,INT2FIX,..), for floats/doubles 
there is NUM2DBL (ruby to c) and rb_float_new() (C to ruby). 

Also, every method in ruby must return value, so if your function does not 
return anything, you have to explicitly return 'nil' with

  return Qnil;

Jan