| Module | Enumerable |
| In: |
vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb
vendor/rails/activesupport/lib/active_support/json/encoders/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