From: Ryan Davis <ryand-ruby@...>
Date: 2007-11-27T10:13:57+09:00
Subject: Re: C-Core-Questions


On Nov 26, 2007, at 02:22 , <saladin.mundi@gmx.de>  
<saladin.mundi@gmx.de> wrote:

> class X
>   $globvar = "hey"  <- setting/instanciation of a global variable
>   def hello
>     hi = "hi"   <- setting/instancition of a local variable
>    end
> end

AFAIK, there is NO hook available for notification of setting gvars.

There is NO hook available for notification of setting local  
variables...

Your code above looks like:

> s(:class,
>  :X,
>  nil,
>  s(:scope,
>   s(:block,
>    s(:gasgn, :$globvar, s(:str, "hey")),
>    s(:defn,
>     :hello,
>     s(:scope, s(:block, s(:args), s(:lasgn, :hi, s(:str, "hi"))))))))

to the parser. All of that code is executed in eval.c and if you look  
at rb_eval you'll notice that NODE_LASGN very cleanly just sets the  
value in the lvar table:

       case NODE_LASGN:
	if (ruby_scope->local_vars == 0)
	    rb_bug("unexpected local variable assignment");
	result = rb_eval(self, node->nd_value);
	ruby_scope->local_vars[node->nd_cnt] = result;
	break;

I will say this one additional thing... USUALLY when I have people  
asking about "the name of the variable" or hooks on assignment etc, it  
is a hint of a bad design smell... What they're generally asking is a  
side effect of something that can be much more gracefully handled with  
a different design.