getting Object#inspect back

[OliverMarchand]

Hello everybody,

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?

Neither option I considered seems suitable:

alias_method --- too late, the original method is gone
instance_eval --- didn't work for me
using .method and .call --- I never seemed to link the objects self to
the Object#inspect method

I am sure it is very easy...
Oliver

 

[Tomasz Wegrzanowski]

Hello everybody,

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?

Neither option I considered seems suitable:

alias_method --- too late, the original method is gone
instance_eval --- didn't work for me
using .method and .call --- I never seemed to link the objects self to
the Object#inspect method

This is tricky, because Object#inspect calls to_s.
You need to copy both.

class Foo < Hash
define_methodinspect, Object.instance_methodinspect))
define_methodto_s, Object.instance_methodto_s))
end

a = Foo.new
p a # => #<Foo:0xb7d26d2c>

If you want to keep Hash to_s (but why would anyone want that)
you can do:

class Foo < Hash
define_methodinspect, Object.instance_methodto_s))
end

 

[dblack]

Hi --

Hello everybody,

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?

Neither option I considered seems suitable:

alias_method --- too late, the original method is gone
instance_eval --- didn't work for me
using .method and .call --- I never seemed to link the objects self to
the Object#inspect method

I am sure it is very easy...

super might be adequate:

def inspect
super
end

unless there are multiple overridings along the way, in which case you
might need:

Object.instance_methodinspect).bind(self).call


David

--
David A. Black | (e-mail address removed)
Author of "Ruby for Rails" [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog) [2] | Co-director, Ruby Central, Inc. [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com | [4] http://www.rubycentral.org

 

[Mauricio Fernandez]

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_methodinspect).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_methodto_s).bind(o).call }
ins[a] # => "#<Hash:0xa7dc63cc>"
ins[[]] # => "#<Array:0xa7dc6200>"
ins[Object.new] # => "#<Object:0xa7dc60fc>"

e.g.

class Hash; define_methodinspect, Object.instance_methodto_s)) end
{} # => #<Hash:0xa7ddec38>

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

a = {}
ins = lambda{|o| Object.instance_methodto_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.