From: Mauricio Fernandez <mfp@...>
Date: 2006-10-12T23:37:08+09:00
Subject: Re: getting Object#inspect back

On Thu, Oct 12, 2006 at 11:07:42PM +0900, dblack@wobblini.net wrote:
> >Not that I despreately need it, but I was wondering how to e.g. get the
> >Object#inspect method back for some classes which override it, say just
> >as an example for a Hash?
> >
[...]
> 
> super might be adequate:
[...] 
> unless there are multiple overridings along the way, in which case you
> might need:
> 
>   Object.instance_method(:inspect).bind(self).call

It's not enough in this case because there's an explicit check in
rb_obj_inspect that will make it use #to_s if the object is not a "regular
one" (i.e. not Array, Hash, File, etc. nor derived classes):

    static VALUE
    rb_obj_inspect(VALUE obj)
    {
	if (TYPE(obj) == T_OBJECT
	    && ROBJECT(obj)->iv_tbl
	    && ROBJECT(obj)->iv_tbl->num_entries > 0) {
	/* .... */
	}
	return rb_funcall(obj, rb_intern("to_s"), 0, 0);
    }

So even if you rebind Object#inspect, it won't do what the OP wanted, but you
can rebind Object#to_s:

    a = {}
    a.inspect                           # => "{}"
    ins = lambda{|o| Object.instance_method(:to_s).bind(o).call }
    ins[a]                              # => "#<Hash:0xa7dc63cc>"
    ins[[]]                             # => "#<Array:0xa7dc6200>"
    ins[Object.new]                     # => "#<Object:0xa7dc60fc>"

e.g.

    class Hash; define_method(:inspect, Object.instance_method(:to_s)) end
    {}                                  # => #<Hash:0xa7ddec38>

However, Object#to_s doesn't display instance variables the way Object#inspect
does: 

    a = {}
    ins = lambda{|o| Object.instance_method(:to_s).bind(o).call }
    a.instance_variable_set :@a, 1
    ins[a]                              # => "#<Hash:0xa7d93490>"
    o = Object.new
    o.instance_variable_set :@a, 1
    o.inspect                           # => "#<Object:0xa7d93364 @a=1>"
    ins[o]                              # => "#<Object:0xa7d93364>"


so you'd have to implement another inspect, with recursivity checks and
everything, if you want to imitate Object#inspect.

-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby