From: dblack@...
Date: 2007-08-26T09:26:11+09:00
Subject: Re: class X < Hash ...  how do I do X.new { |hash, key| ...} ?

Hi --

On Sun, 26 Aug 2007, Larry Fast wrote:

> I created a child class of Hash and would like to internalize the
> equivalent of Hash.new {|hash,key| }  The following code failed:
>
> class X < Hash
>  def initialize
>    super { |hash,key|  ... }
>  end
> end
>
> Any suggestions?  I suppose I could do it externally with a create()
> wrapper but it doesn't seem very pragmatic.
>
> def create_X
>   y = X.new {|hash,key|  ... }
>   return y
> end
>
> My overall goal is to record a list of attempts to read undefined Keys.

Here's what I did -- I'm not sure how it differs from yours but
hopefully it will help:

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]


David

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