From: Josh Cheek <josh.cheek@...>
Date: 2011-06-21T02:37:45+09:00
Subject: Re: What about Object#to_ruby ?

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On Mon, Jun 20, 2011 at 7:40 AM, Bernard Lambeau <blambeau@gmail.com> wrote:

> Hi!
>
> It's not the first time that I need a to_ruby method which would guarantee
> the following invariant:
>
>  Kernel.eval(foo.to_ruby) == foo
>
> It actually works when using inspect with most basic objects (Integer,
> String,
> True & FalseClass, etc.), without actually being the specification of
> inspect.
>
> I admit that such a feature probably only makes sense for classes that
> actually
> capture datatypes, whose instances are then true values.
>
> Does anyone know a gem that provides such a feature? To your knowledge,
> would to_ruby be a conflicting name with existing gems in the ecosystem
> or future plans for ruby itself?
>
> Just in case you ask yourself whether this feature is needed, have a look
> at rubygems itself:
>
> https://github.com/rubygems/rubygems/blob/master/lib/rubygems/specification.rb#L1899-1915
>
> Thanks for any suggestion,
> Bernard
>
> --
> PhD Student, Computer Science Department, EPL/INGI, UCLouvain, Belgium
> Mail:    blambeau@gmail.com
> Mobile:  +32 477 24 58 61
> Blog:    http://revision-zero.org/
> Code:    http://github.com/blambeau/
> Follow:  http://twitter.com/blambeau/
>

# I think the following works for everything except data that contains code
itself (closures / methods)

Datum = Struct.new :some_attribute

data = [
  Datum.new("string"),
  Datum.new(1234),
  Datum.new(/regex/),
]


serial = Marshal.dump data
serial                        # =>
"\x04\b[\bS:\nDatum\x06:\x13some_attributeI\"\vstring\x06:\x06ETS;\x00\x06;\x06i\x02\xD2\x04S;\x00\x06;\x06I/\nregex\x00\x06;\aF"
Marshal.load(serial) == data  # => true

require 'yaml'
serial = YAML.dump data
serial                        # => "--- \n- !ruby/struct:Datum \n
 some_attribute: string\n- !ruby/struct:Datum \n  some_attribute: 1234\n-
!ruby/struct:Datum \n  some_attribute: !ruby/regexp /regex/\n"
YAML.load(serial) == data     # => true

---

I think the closest things that exist right now that would be able to do
this for closures as well, would be some of Ryan Davis' tools (last I heard,
they don't work on 1.9, though):
https://rubygems.org/gems/ruby2ruby
https://rubygems.org/gems/ruby_parser
https://rubygems.org/gems/sexp_processor

Rubinius might also be able to do something like this.


On Mon, Jun 20, 2011 at 12:20 PM, Steve Klabnik <steve@steveklabnik.com>wrote:

> I believe pry has this kind of thing: https://github.com/banister/pry
>
> From its readme:
>
> pry(Pry):1> show-method rep -l
>
> From: /home/john/ruby/projects/pry/lib/pry/pry_instance.rb @ line 143:
> Number of lines: 6
>
> 143: def rep(target=TOPLEVEL_BINDING)
> 144:   target = Pry.binding_for(target)
> 145:   result = re(target)
> 146:
> 147:   show_result(result) if should_print?
> 148: end
>

I'm admittedly uninformed, but I think they do this by keeping track of
where methods get defined, then opening that file and reading that
definition (as opposed to introspecting on the object itself) in the example
above, for instance, they also report the file and line numbers of the rep
method.

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