From: umptious@...
Date: 2006-12-07T08:55:10+09:00
Subject: Problem with Marshaling WeakRefs?

I'm experimenting with Marshal, but I'm having problems making it work
with data structures that use WeakRefs. Marshal saves without
complaining, but the WeakRefs seem to be junk when I load. Hopefully
the program below explains everything. I'm using Ruby 184-15 on Windows
XP Pro.

Am I missing something?

----------------------------------------------------------------------------------------------------------------------------

#!/usr/bin/env ruby

require "WeakRef"

save = false

class Box
    def initialize()
        @things = []
    end

    def add(q)
        @things.push q
        q.set_owner(self)
    end

  attr_reader :things
end

class Pen
    def initialize(name)
        @name = name
        @owner = nil
    end
    def set_owner(owner)
        @owner = WeakRef.new(owner)
    end
    attr_reader(:name, :owner)
end

if save
    box = Box.new()
    [Pen.new("Parker 51"), Pen.new("Densho"), Pen.new("Snorkel")].each{
|q| box.add(q) }
    File.open('marsh.txt', "w") do |f|
        Marshal.dump(box, f)
    end
else
    File.open("marsh.txt") do |f|
       box = Marshal.load(f)
    end
end

p box.things[0].owner # Error occurs here...

#c:/ruby/lib/ruby/1.8/WeakRef.rb:64:in `_id2ref': no implicit
conversion
# from nil to integer (TypeError)
#	from C:/RubyCode/Adventure.04/scratch.rb:47:in `p'
#	from C:/RubyCode/Adventure.04/scratch.rb:47