From: Brian Candler <B.Candler@...>
Date: 2003-05-04T01:29:49+09:00
Subject: Re: [Q] eval and binding with mod_ruby

On Fri, May 02, 2003 at 07:43:42AM +0900, kwatch wrote:
> view.rhtml
>   .--------------------
>   Hello <%= username %>!
>   .--------------------
> 
> logic.rbx
>   .--------------------
>   require 'cgi'
>   cgi = CGI.new
>   print cgi.header
>   
>   require 'eruby'
>   username = 'Ruby'
>   ERuby::import('view.rhtml')	# no binding(), but evaled with no error.
>   .--------------------
> 
> I have read ERuby source code (eruby_load() in eruby_lib.c),
> but I could not get understand how ERuby do.
> 
> Would you teach me if you know it?

I don't :-) But I have just installed eruby now...

I've played with this a bit and have been unable to make the local variable
'username' available in viewloader.rb without passing a binding explicitly
as you did - having tried various combinations of instance_eval, passing in
'self' as a parameter etc.

The usual rule is that when you call a method, a new scope is started (so
local variables in the calling method are not visible in the called method).
I don't understand how or why ERuby::import is able to see them when it
calls 'eval'. The relevant function in eruby_lib.c looks like

static VALUE eruby_import(VALUE self, VALUE filename)
{
    VALUE compiler, file, code;

    compiler = eruby_compiler_new();
    file = rb_file_open(STR2CSTR(filename), "r");
    code = eruby_compiler_compile_file(compiler, file);
    rb_funcall(ruby_top_self, rb_intern("eval"), 3, code, Qnil, filename);
    return Qnil;
}


And the closest I can get to simulate that is:

-----------------------------------
  TOP_SELF = self

  module Foo
  def Foo.output(code)
    TOP_SELF.send( :eval, code )
  end
  end

  username="test"
  Foo.output("puts username")
-----------------------------------

but this doesn't work :-( Anybody else got any better ideas, or an
explanation of why ERuby doesn't need you to pass in an explicit 'binding'?

Thanks,

Brian.