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" => <Person ...>, "chade-" => <Person ...>, ...}
# people.index_by { |person| "#{person.first_name} #{person.last_name}" }
# => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
#
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.
def several?
size > 1
end
end