Module | Enumerable |
In: |
vendor/rails/activesupport/lib/active_support/json/encoders/enumerable.rb
vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb |
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"
# File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 20 20: def group_by 21: inject ActiveSupport::OrderedHash.new do |grouped, element| 22: (grouped[yield(element)] ||= []) << element 23: grouped 24: end 25: 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 ...>, ...}
# File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 63 63: def index_by 64: inject({}) do |accum, elem| 65: accum[yield(elem)] = elem 66: accum 67: end 68: end
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)
# File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 46 46: def sum(identity = 0, &block) 47: return identity unless size > 0 48: 49: if block_given? 50: map(&block).sum 51: else 52: inject { |sum, element| sum + element } 53: end 54: end