From: Joel VanderWerf <vjoel@...>
Date: 2006-02-08T05:39:16+09:00
Subject: Re: marshalling constants

Brian Buckley wrote:
> Hello,
> 
> When one marshals a constant and later unmarshals it, a brand new object
> appears to be created during unmarshalling.  This seems wasteful, especially
> in cases when constants are large (contain many attributes).  Is it possible
> to customize marshal for a class (or for singleton objects of the class) so
> that unmarshalling a constant simply returns the already existing constant
> rather than creating a new one?  I've noticed Fixnum's exhibit this
> behavior.
> 
> --Brian
> 
> class A;
>   A1 = A.new
> end
> 
> before = A::A1
> after = Marshal.load(Marshal.dump(before)) #marshal and back
> puts before == after  #darn -- it is false
> puts before.object_id == after.object_id  #same here

class A
  A1 = new

  def self.name_for_constant obj
    @name_for_constant ||= {}
    @name_for_constant[obj] ||= constants.find {|c| const_get(c) == obj}
  end

  def _dump(limit)
    self.class.name_for_constant(self)
  end

  def self._load(str)
    const_get str
  end
end

before = A::A1
after = Marshal.load(Marshal.dump(before)
puts before == after                      # ==> true
puts before.object_id == after.object_id  # ==> true


-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407