From: Sean O'Halpin <sean.ohalpin@...>
Date: 2005-10-18T07:09:57+09:00
Subject: Re: declaratively caching results of a method

On 10/17/05, Daniel Berger <Daniel.Berger@qwest.com> wrote:
> Eh? If you memoize in initialize, why wouldn't another instance of Foo get the
> benefit?

Try it:

class Foo
  include Memoize
  def initialize
    memoize :foo
  end
  def foo(*args)
    puts "calculating #{self}.foo(#{args.map{|x| x.inspect}.join(',')})"
    args.inject(0) {|sum, x| sum + x}
  end
end

f = Foo.new
puts f.foo(2)
puts f.foo(2)

g = Foo.new
puts g.foo(2)


__END__
calculating #<Foo:0x28705e8>.foo(2)
2
2
calculating #<Foo:0x28703d8>.foo(2)
2

It's because you're defining the memoized method on the singleton class:

    (class << self; self; end).class_eval do ... end

Regards,

Sean