From: ahoward <ahoward@...>
Date: 2003-06-01T01:38:06+09:00
Subject: Re: Marshaling

On Sat, 31 May 2003, Dominik Werder wrote:

> Hi there,
>
> I need to dump some objects but they have references to files. These
> references are not important and could be discarded before serialization so
> that no TypeError raises. But if I write my _dump method to do this, I need
> to make the complete serialization on my own :(((
> Is there a way to mark variables not to be marshaled?
> How do you solve this problem?

i *just* had this same problem yesterday... here's the two approaches i
figured out, kind of hacky, but they work:

/usr/home/howardat/eg/ruby > cat marshal.rb
#!/usr/bin/env ruby

class Foo
  attr_accessor :io
  attr_accessor :p
  attr_accessor :m
  def initialize p=__FILE__, m='w'; @io = open (@p=p), (@m=m); end
end

f = Foo.new
f.io = nil
p Marshal.load Marshal.dump f

class Bar < Foo
  attr_accessor :args
  def initialize(*args)
    @args = args
    super *args
  end
  def _dump d
    Marshal.dump args
  end
  class << self
    def _load s
      new *(Marshal.load s)
    end
  end
end

b = Bar.new __FILE__, 'w'
p Marshal.load Marshal.dump b

/usr/home/howardat/eg/ruby > ruby marshal.rb
#<Foo:0x40182af0 @io=nil, @m="w", @p="marshal.rb">
#<Bar:0x401827e4 @io=[#<File:0x40182780>, "w"], @args=["marshal.rb", "w"], @m="w", @p="marshal.rb">


the first method 'marks' vars not to be dumped with nil, the other remembers
the args passed to initialize and simply re-creates the object.  note that you
cannot (easily) use _dump() to do the first since

  def _dump depth
    @dont_dump = nil
    Marshal.dump self
  end

will recurse.


an argument to Marshal.dump, which meant 'mark anything which cannot be dumped
as nil' would be most useful IMHO...

-a
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