From: Josh Cheek <josh.cheek@...>
Date: 2011-05-23T02:11:57+09:00
Subject: Re: Ruby Clasess

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class Animal

  def self.inherited(subclass)
    children << subclass
  end

  def self.children
    @children ||= []
  end

  def self.descendants
    children.map do |child|
      [child].concat child.descendants
    end.flatten
  end

end

Dog    =  Class.new Animal
Cat    =  Class.new Animal
Tabby  =  Class.new Cat

RUBY_VERSION        # => "1.9.2"
Animal.children     # => [Dog, Cat]
Animal.descendants  # => [Dog, Cat, Tabby]

Cat.descendants     # => [Tabby]

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