Rails - Nov 2006 - Array#group_by

Just thought I''d share a function which has been really useful to me,
for 2
reasons

1) It could easily help someone else
2) People might be able to make it work better or point out where it''s
not
optimal

class Array
  # Groups elements of an array based on a user-defined condition
  # 
  # Each element from this array is passed to the block, and the returned value
  # determines the key under which it will be stored in the output hash
  #
  # If no block is given then the array indices will be used as the hash keys
  def group_by
    hsh = {}
    self.dup.each_with_index do |element, i|
      if block_given?
        key = yield element
      else
        key = i
      end
      hsh[key] ||= []
      hsh[key] << element
    end
    hsh
  end
end


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Gareth Adams wrote:
> Just thought I''d share a function which has been really useful to
me,
> for 2
> reasons
> 
> 1) It could easily help someone else
> 2) People might be able to make it work better or point out where
it''s
> not
> optimal
> 
This has already been done: Enumerable::group_by() that I believe is 
shipping with Rails 1.2. (ActiveSupport:Enumeration).  It appears that 
others shared your train of thought.. :)

ilan

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