From: Justin Collins <justincollins@...>
Date: 2009-02-18T05:32:52+09:00
Subject: Re: Marshal.dump fails on extended OpenStruct

synergism wrote:
> If I subclass OpenStruct and extend the subclass, I cannot
> Marshal.dump it.  This is apparently because ostruct.rb has its own
> custom marshal_dump / marshal_load that only cares about what's in
> @table:
>
>   def marshal_dump
>     @table
>   end
>   def marshal_load(x)
>     @table = x
>     @table.each_key{|key| new_ostruct_member(key)}
>   end
>
> Is there no way to fix this in ostruct.rb to allow my 'bad' example
> below to work?
>
> require 'pp'
> require 'ostruct'
>
> case ARGV.first
>     when /bad/i,nil
>         class C < OpenStruct
>             def initialize
>                 super()
>                 @var=123
>             end
>         end
>     when /good/i
>         class C
>             def initialize
>                 @struct=OpenStruct.new
>                 @var=123
>             end
>
>             def method_missing method,*args,&block
>                 @struct.send method,*args,&block
>             end
>         end
> end
>
> c=C.new
> c.a=:a
> pp c
> puts 'c.a=%s ' %  c.a
> puts 'c var=%s' % c.instance_variable_get('@var')
> x=Marshal.load(Marshal.dump(c))
>
> pp x
> puts 'x.a=%s ' %  x.a
> puts 'x var=%s' % x.instance_variable_get('@var')
>
>   


You could just write new marshal_dump and marshal_load methods:

require 'ostruct'
require 'pp'
class C < OpenStruct

  def initialize *args 
    super       
    @var = 123  
  end   

  def marshal_dump
    [@table, Hash[self.instance_variables.map { |v| [v, self.instance_variable_get("#{v}")] }]]
  end   

  def marshal_load x
    @table = x[0]
    @table.each_key{|key| new_ostruct_member(key)}
    x[1].each do |k,v|
      self.instance_variable_set("#{k}", v) unless k.to_sym == :table
    end         
  end   
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' %  c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' %  x.a
puts 'x var=%s' % x.instance_variable_get('@var')



-Justin