From: Brian Candler <b.candler@...>
Date: 2010-10-15T04:16:34+09:00
Subject: Re: <Class info> from a String.

Huw Taylor wrote in post #950237:
> If I were to have this:
>
> class Hew
>   def initialize(string)
>     @string = string
>   end
>   def other_method
>   end
> end
>
> a = Hew.new("Broown Cew")
> => #<Hew:0x40e8238 @string = "Broown Cew">
>
> b = a.to_s
> => "#<Hew:0x40e8238>"
>
> My question is: Is there anyway to get the class (and its info) from b
> (i.e what is now a string)?

Maybe you're looking for ObjectSpace._id2ref

Unfortunately, the hex pointer shown by #inspect doesn't always map 
directly to the object's object_id, and I think the algorithm to map it 
varies with the version of ruby you're running :-(

But here in principle is how you recover a reference to the object:

>> RUBY_DESCRIPTION
=> "ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]"
>> a = Hew.new("Broown Cew")
=> #<Hew:0x7f7b6ea152e8 @string="Broown Cew">
>> a.object_id.to_s(16)
=> "3fbdb750a974"
>> (a.object_id << 1).to_s(16)
=> "7f7b6ea152e8"
>> b = ObjectSpace._id2ref(Integer("0x7f7b6ea152e8") >> 1)
=> #<Hew:0x7f7b6ea152e8 @string="Broown Cew">
>> a.eql?(b)
=> true

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