From: Logan Capaldo <logancapaldo@...>
Date: 2007-05-04T23:44:45+09:00
Subject: Re: Beyond YAML? (scaling)

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On 5/4/07, Bil Kleb <Bil.Kleb@nasa.gov> wrote:
>
> William James wrote:
> >
> > Would making a copy of the hash use too much
> > memory or time?
>
> I don't know, but that's surely another way out of
> the Marshal-hash-proc trap...
>
> Thanks,
> --
> Bil Kleb
> http://fun3d.larc.nasa.gov
>
>
I dunno how safe it is to rely on this behavior, but calling Hash#default=
strips the proc and makes the hash marshallable:

>> h = Hash.new { |h,k| h[k] = [] }
=> {}
>> h["a"]
=> []
>> h
=> {"a"=>[]}
>> h["b"] = 7
=> 7
>> h
=> {"a"=>[], "b"=>7}
>> h.default = nil
=> nil
>> h
=> {"a"=>[], "b"=>7}
>> Marshal.dump h
=> "\004\b{\a\"\006a[\000\"\006bi\f"

of course this means you won't get your default proc back when you load the
hash and mutate it. However:
db = Marshal.load( from_disk )
delta = Hash.new { |h, k| h[k] = if db.has_key? k then db[k] else [] end }
delta["foo"] = "add a new value"
delta["bar"] << "update something in the original"
... more of the same ...
to_disk = Marshal.dump( db.merge!( delta ) )

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