From: Stefano Crocco <stefano.crocco@...>
Date: 2007-01-25T01:01:01+09:00
Subject: Re: ebedded: calling a C function from script.

Alle 16:25, mercoled� 24 gennaio 2007, Shea Martin ha scritto:
> Shea Martin wrote:
> > Thanks, that worked great.  How do I do I define a class method? Doesn't
> > seem to be in ruby book.
> > ~S
>
> Also, I can't seem to figure out how to pass ARGV to my script.  I tried
> setting the global AGV before running, but it gets reset when I start.
>
> ~S

You should use the ruby_options C function. 

To define a class method, you should first define a class. This is done using 
the rb_define_class function. It takes two parameters, the name of the class 
(as a char*) and the superclass (as a VALUE, not its name). For instance, if 
you want to define the class MyClass, as a subclass of Object, you'd do:

rb_define_class("MyClass", rb_cObject);

rb_cObject is a C global variable of type VALUE which corresponds to the ruby 
Object class. rb_define_class returns a VALUE corresponding to the new class. 
With it, you can define both instance methods and class methods.

To define a class method you should use rb_define_module_function, while to 
define an instance method, you'd use the rb_define_method function. They both 
takes four arguments: the class or module (the value returned by 
rb_define_class, for instance), the name of the method, a pointer to the C 
function which implements the method and the number of arguments this C 
function takes (including the self argument).

A complete example (again, untested):

static VALUE _class_method(VALUE self, VALUE arg){
//Do something here and return a VALUE or Qnil
}

static VALUE _instance_method(VALUE self){
//Do something else here and return a VALUE or Qnil
}

void InitMyClass(){
  VALUE cls=rb_define_class("MyClass", rb_cObject);
  rb_define_module_function(cls, "a_class_method", _class_method, 2);
  rb_define_method(cls, "an_instance_method", _instance_method, 1);
}

Stefano