From: Michael Fellinger <m.fellinger@...>
Date: 2009-03-03T02:32:30+09:00
Subject: Re: Marshal.load does not create new instances?

On Sat, Feb 28, 2009 at 8:56 AM, Ian Trudel <ian.trudel@gmail.com> wrote:
> Marshal does not seem to instantiate given class(es) on load. Moreover,
> it will absolutely work as long as the class is define but even if it
> has no attributes. The following code snippet creates an array with
> filled with objects:
>
> class Data
> end
>
> data = File.open("data.bin", "rb") { |f| Marshal.load(f) }
>
> This absolutely works fine even if the Data class used to dump (e.g.
> from another program) has many instance variables. They just won't be
> accessible directly (but still can be accessible using reflection).
> Inspect would show something like <Data:0x2b24088 @name="Account"
> @expanded=true ..>. Furthermore, it doesn't seem to use the defined
> class if an IO is fed in Marshal.load, thus overriding Data._load just
> won't work. Is that the expected behaviour?
>
> This is really annoying considering that I would like to load data onto
> one (among many) version of Data class. The version of the class to be
> used is determined and set at run-time according to the file loaded;
> this is my ultimate goal. There is obviously no cast feature in Ruby.
> Even using a proxy won't cut it, if only for the fact that Marshal
> doesn't instantiate loaded data.

http://eigenclass.org/R2/writings/extprot-vs-ruby-marshal

^ manveru