From: Gaspard Bucher <gaspard@...>
Date: 2007-09-14T23:08:58+09:00
Subject: Race condition in class inheritance

I need to identify classes from a string called kpath (class path)
reflecting the class inheritance. The string is made of the first
letter of each class. This is what I have now:
class Node
  @@classes = {'N' => self}
  def self.inherited(child)
    super
    @@classes[child.kpath] = child
  end

  def self.kpath
    self == Node ? ksel : (superclass.kpath + ksel)
  end

  def self.ksel
    self.to_s[0..0]
  end

  def self.class_from_kpath(kpath)
    @@classes[kpath]
  end
end

class Page < Node
end

class Document < Page
end

class Draft < Page
  def self.ksel
    'A'
  end
end

puts Node.class_from_kpath('N')    # got 'Node', ok.
puts Node.class_from_kpath('NPD') # wanted 'Document', got 'Draft'
puts Node.class_from_kpath('NPA') # wanted 'Draft', got nil

I understand that Draft's ksel method is not known at the time
Node.inherited is called.

How can I have Node.inherited being called once the complete child
class is built ?

Thanks for your answers.
Gaspard