Some Ruby Array methods

gistfile1.rb

class Array
  def pinject(memo, &block)
    inject(memo) { |all, curr| block.call(all, curr); all }
  end

  def hash_by
    return {} unless block_given?
    
    pinject({}) { |all, curr|
      # yield = block to extract key from an item
      key = yield(curr)
      all[key] = curr if key
    }
  end

  def grouped_hash_by
    return {} unless block_given?
    
    pinject({}) { |all, curr|
      # yield = block to extract key from an item
      (all[yield(curr)] ||= []) << curr
    }
  end
end