From: Joakim Andersson <tyrak@...>
Date: 2002-02-18T03:32:52+09:00
Subject: Problems with Ruby in C

Hi, 

I'm having a problem with getting instance_eval to do what I want it to
do when I'm calling ruby from C. I've created a small ruby program and
my c version of the same, both are included below, which illustrate the
problem.

The Ruby program does what is expected but the C program doesn't, so I'm
hoping that some kind soul could tell me what I'm doing wrong.

This is the Ruby program I'm trying to do in C:

class Context
  def execute(str)
    instance_eval(str)
  end
end

a = Context.new()
a.execute("a = 5 ; puts a")

b = Context.new()
b.execute("puts a")

When running this program I get:
5
test5.rb:4:in `instance_eval': (eval):1:in `instance_eval': undefined 
    local variable or method `a' for #<Context:0x4021c278> (NameError)
        from test5.rb:4:in `instance_eval'
        from test5.rb:4:in `execute'
        from test5.rb:12

which is what I expected.

My C version of the same program looks like this:

#include "ruby.h"

static VALUE cContext_execute(VALUE self, VALUE str)
{
    return rb_funcall(self, rb_intern("instance_eval"), 1, str);
}

int main(void)
{
    VALUE cContext, a, b;
    
    ruby_init();
    
    cContext = rb_define_class("Context", rb_cObject);
    rb_define_method(cContext, "execute", cContext_execute, 1);
    
    a = rb_class_new_instance(0, NULL, cContext);
    rb_funcall(a, rb_intern("execute"), 1, rb_str_new2("a = 5 ; puts a"));

    b = rb_class_new_instance(0, NULL, cContext);
    rb_funcall(b, rb_intern("execute"), 1, rb_str_new2("puts a"));

    return 0; 
}

But then running this program I get:
5
5


Thanks and regards,
Joakim

-- 
Joakim Andersson ; tyrak@borgship.net ; http://borgship.net/~tyrak/