From: "ara.t.howard" <ara.t.howard@...>
Date: 2008-09-18T04:43:40+09:00
Subject: Re: Singleton class's original class


On Sep 17, 2008, at 1:23 PM, Paul Brannan wrote:

> Given a singleton class:
>
>  irb(main):001:0> class Foo
>  irb(main):002:1>   def self.singleton_class
>  irb(main):003:2>     return class << self; self; end
>  irb(main):004:2>   end
>  irb(main):005:1> end
>  => nil
>  irb(main):006:0> sc = Foo.singleton_class
>  => #<Class:Foo>
>
> How can I get class that the singleton class is a singleton class of?
>
> (and is there a name for this?)

it might not be a class... but will this work?


cfp:~ > cat a.rb
class Object
   def singleton_class &block
     sc =
       class << self
         self
       end

     unless sc.respond_to?(:parent)
       parent_id = self.object_id #Module === self ? self : self.class
       sc.instance_eval "def parent()  
ObjectSpace._id2ref(#{ parent_id }) end"
     end

     block ? sc.module_eval(&block) : sc
   end
end

p File.singleton_class.parent
p Array.new.singleton_class.parent
p Hash.new.singleton_class.parent

p Hash.new.singleton_class{ parent }
p Hash.singleton_class{ parent }


options = { :key => :value }

options.singleton_class do
   def getopt opt
     fetch(opt.to_s.to_sym) rescue fetch(opt.to_s)
   end
end

p options.getopt(:key)


cfp:~ > ruby a.rb
File
[]
{}
{}
Hash
:value


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