From: Pit Capitain <pit.capitain@...>
Date: 2008-07-16T16:13:34+09:00
Subject: Re: Complicated class initialization/instantiation problem.

2008/7/16 Michael T. Richter <ttmrichter@gmail.com>:
> Basically I'm relying on several non-DRY chunks of code, each of which
> can cause me problems in the future.  First, in each of the Foo* classes
> I'm repeating ".each { |tag| Bar.register(tag, Foo1) }".
> (...)
> The second, more subtle,
> problem is exemplified in Foo2.  Because the code is mostly boilerplate
> -- I'm changing the tags and the instantiating class only -- it's very
> easy to make a cut-and-paste bug like telling the registry to
> instantiate Foo1 instead of Foo2 for tags 4, 5 and 6.

Hello Michael, to remove the each loop you could change Bar.register
to accept multiple tags, and to avoid copy and paste errors you could
just use "self" instead of the classes:

  class Bar
    @registry = {}
    def self.register klass, *tags
      tags.each do |tag|
        @registry[tag] ||= klass
      end
    end
    # other stuff
  end

  class Foo1
    Bar.register self, TAG1 = 1, TAG2 = 2, TAG3 = 3
    # other stuff
  end

  class Foo2
    Bar.register self, TAG4 = 4, TAG5 = 5, TAG6 = 6
    # other stuff
  end

Regards,
Pit