From: Larry Fast <lfast@...>
Date: 2007-08-27T05:24:31+09:00
Subject: Re: class X < Hash ...  how do I do X.new { |hash, key| ...}

Thank you both. Yes, that works. So I'm puzzled by the error I was 
getting. Oh well, carrying on...

I still have a related problem.  I'm using YML to export and import my 
Hash. YML loses all the Hash initialization settings.  So I may still 
have to create a new internal Hash after reloading from YML.

class X < Hash
   attr_accessor :attempts
   def initialize
     self.attempts = []
     super {|h,k| attempts << k unless h.has_key?(k); nil }
   end
end

h = X.new
h[1] = 2
p h[1]          # 2
p h[0]          # nil
p h[2]          # nil
p h.attempts    # [0,2]

yml_text = YAML.dump(h)   # "--- !map:X \n1: 2\n"
j = YAML.load(yml_text)   # {1=>2}
j.class                   # X
j.attempts                # nil
j[2] = 25                 # 25
j                         # {1=>2, 2=>25}
j[3]                      # nil
j.attempts                # nil
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