From: Brian Buckley <briankbuckley@...>
Date: 2005-10-18T03:57:51+09:00
Subject: Re: declaratively caching results of a method

> You could check out Daniel Berger's memoize (based on Nobu Nokada's
> original I think) on RAA (http://raa.ruby-lang.org/project/memoize/).

Thank you and wowser!  memoize seems to do just what I'd been looking
to do.  A handful of lines.  I can see it works.

#my test code
f = Foo.new
f.memoize(:calc1)
f.memoize(:calc2)
f.calc1(1,2,3)
f.calc1(1,2,3) #yep its working
f.calc1(7,8,9) #yep its working

If I can ask a Ruby 101 question about it...  Isn't "cache" in the
module (pasted below in its entirety it is so short) only a local
variable?  Why does is retain state? How can one, for example, access
the cache to see the state of the cache?

Thanks!

--Brian

module Memoize
   MEMOIZE_VERSION = "1.0.0"
   def memoize(name)
      meth = method(name)
      cache = {}
      (class << self; self; end).class_eval do
         define_method(name) do |*args|
            cache[args] ||= meth.call(*args)
         end
      end
  end
end