From: Kenichi Kamiya <kachick1@...>
Date: 2012-02-21T03:11:30+09:00
Subject: Re: array.uniq on specific attributes

# an approach

class Array
  private
 
  def _uniq_by(&block)
    new, memo = [], {}
 
    map(&block).each_with_index do |mapped, idx|
      unless memo[mapped]
        memo[mapped] = true
        new << self[idx]
      end
    end
   
    new
  end
 
  alias_method :_uniq, :uniq
  alias_method :_uniq!, :uniq!
 
  public
 
  def uniq(&block)
    block_given? ? _uniq_by(&block) : _uniq
  end
 
  def uniq!(&block)
    if block_given?
      new = _uniq_by(&block)
 
      if self == new
        nil
      else
        replace(new)
      end
    else
      _uniq!
    end
  end
end

# 1.9.2 original
http://ideone.com/Uygbz

# same return from 1.8.6, 1.8.7, 1.9.2, 1.9.3
http://ideone.com/ySoIE

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