From: "Ara.T.Howard" <ara.t.howard@...>
Date: 2005-11-16T23:07:28+09:00
Subject: Re: static variable; behaviour in ruby?

On Wed, 16 Nov 2005, Hugh Sasse wrote:

> Any idea how to create or simulate a static variable in ruby?
>
> I want to create a variable to hold state between calls of a method,
> but have the state disappear when the method goes out of scope.
> I could create it in some external object but then I'd need to query
> the scoping rules, and know where i was.
>
> I'm trying to do an instance_eval on a string containing a method such as
>   do_this x,y,z {block}
> and I want to evaluate the block, or not, as a function of some
> state against which x,y,z are compared.  The code will be called several
> times, but I only want the state intialized the first time the scope
> is entered.
>
> And, just to make matters worse, there could be several independent
> calls to this method within the scope, each with its own separate
> state.

   harp:~ > cat a.rb
   def do_this_factory x, y, z, &block
     state = rand  # do something with x, y, z
     lambda{ block[x, y, z] if state < 0.42 }
   end

   a = do_this_factory 'x','y','z' do |x,y,z| p [x,y,z] end
   a.call

   harp:~ > ruby a.rb

   harp:~ > ruby a.rb

   harp:~ > ruby a.rb
   ["x", "y", "z"]

   harp:~ > ruby a.rb

   harp:~ > ruby a.rb
   ["x", "y", "z"]

   harp:~ > ruby a.rb
   ["x", "y", "z"]


> Maybe there's another way to do this?

write it in assembler ;-)


-a
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