module Enumerable # Ruby 1.8.7 introduces group_by, but the result isn't ordered. Override it. remove_method(:group_by) if [].respond_to?(:group_by) && RUBY_VERSION < '1.9' # Collect an enumerable into sets, grouped by the result of a block. Useful, # for example, for grouping records by date. # # Example: # # latest_transcripts.group_by(&:day).each do |day, transcripts| # p "#{day} -> #{transcripts.map(&:class).join(', ')}" # end # "2006-03-01 -> Transcript" # "2006-02-28 -> Transcript" # "2006-02-27 -> Transcript, Transcript" # "2006-02-26 -> Transcript, Transcript" # "2006-02-25 -> Transcript" # "2006-02-24 -> Transcript, Transcript" # "2006-02-23 -> Transcript" def group_by inject ActiveSupport::OrderedHash.new do |grouped, element| (grouped[yield(element)] ||= []) << element grouped end end unless [].respond_to?(:group_by) # Calculates a sum from the elements. Examples: # # payments.sum { |p| p.price * p.tax_rate } # payments.sum(&:price) # # The latter is a shortcut for: # # payments.inject { |sum, p| sum + p.price } # # It can also calculate the sum without the use of a block. # # [5, 15, 10].sum # => 30 # ["foo", "bar"].sum # => "foobar" # [[1, 2], [3, 1, 5]].sum => [1, 2, 3, 1, 5] # # The default sum of an empty list is zero. You can override this default: # # [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0) # def sum(identity = 0, &block) return identity unless size > 0 if block_given? map(&block).sum else inject { |sum, element| sum + element } end end # Convert an enumerable to a hash. Examples: # # people.index_by(&:login) # => { "nextangle" => , "chade-" => , ...} # people.index_by { |person| "#{person.first_name} #{person.last_name}" } # => { "Chade- Fowlersburg-e" => , "David Heinemeier Hansson" => , ...} # def index_by inject({}) do |accum, elem| accum[yield(elem)] = elem accum end end end