"Tom Counsell" <tamc2 / cam.ac.uk> schrieb im Newsbeitrag
news:87cd2dd2.0409210238.6414881c / posting.google.com...
> Hello
>
> Can someone help me?  I'm trying to Marshal a class that includes
> 'Singleton' but all I get upon loading is an empty object.
>
> e.g:
> require 'singleton'
> class SingleHash < Hash
> include Singleton
> end
>
> o = SingleHash.instance
> o[1] = 'hello world'
>
> # Save the object to file
> File.open( 'test', 'w' ) { |file| Marshal::dump( o, file ) }
>
> # Leave
> quit
>
> # Restart ruby
> # Redefine SingleHash class
> o = nil
> o = File.open( 'test' ) { |file| o = Marshal::load( file ) }
> puts o[1] #=> nil ? Why didn't the contents get written to the file?
>
> Apologies if it is obvious, but why didn't the contents of the class
> get written to / reloaded from the file?  Is there any way to make
> this work?

Because you can have only one instance of a singleton class marshalling
and loading is disabled.  You can use delegation, store the hash and
update with the hash if you like.  Or you just don't make it a singleton,
which is probably more appropriate in this case.

Kind regards

    robert