require 'active_support/ordered_hash' 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 assoc = ActiveSupport::OrderedHash.new each do |element| key = yield(element) if assoc.has_key?(key) assoc[key] << element else assoc[key] = [element] end end assoc 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 # Iterates over a collection, passing the current element *and* the # +memo+ to the block. Handy for building up hashes or # reducing collections down to one object. Examples: # # %w(foo bar).each_with_object({}) { |str, hsh| hsh[str] = str.upcase } #=> {'foo' => 'FOO', 'bar' => 'BAR'} # # *Note* that you can't use immutable objects like numbers, true or false as # the memo. You would think the following returns 120, but since the memo is # never changed, it does not. # # (1..5).each_with_object(1) { |value, memo| memo *= value } # => 1 # def each_with_object(memo, &block) returning memo do |m| each do |element| block.call(element, m) end end end unless [].respond_to?(:each_with_object) # 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 # Returns true if the collection has more than 1 element. Functionally equivalent to collection.size > 1. # Works with a block too ala any?, so people.many? { |p| p.age > 26 } # => returns true if more than 1 person is over 26. def many?(&block) size = block_given? ? select(&block).size : self.size size > 1 end # Returns true if none of the elements match the given block. # # success = responses.none? {|r| r.status / 100 == 5 } # # This is a builtin method in Ruby 1.8.7 and later. def none?(&block) !any?(&block) end unless [].respond_to?(:none?) end