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

Methods

Public Instance methods

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

[Source]

    # File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 79
79:   def each_with_object(memo, &block)
80:     returning memo do |m|
81:       each do |element|
82:         block.call(element, m)
83:       end
84:     end
85:   end

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"

[Source]

    # File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 22
22:   def group_by
23:     assoc = ActiveSupport::OrderedHash.new
24: 
25:     each do |element|
26:       key = yield(element)
27: 
28:       if assoc.has_key?(key)
29:         assoc[key] << element
30:       else
31:         assoc[key] = [element]
32:       end
33:     end
34: 
35:     assoc
36:   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 ...>, ...}

[Source]

    # File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 94
94:   def index_by
95:     inject({}) do |accum, elem|
96:       accum[yield(elem)] = elem
97:       accum
98:     end
99:   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.

[Source]

     # File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 103
103:   def many?(&block)
104:     size = block_given? ? select(&block).size : self.size
105:     size > 1
106:   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)

[Source]

    # File vendor/rails/activesupport/lib/active_support/core_ext/enumerable.rb, line 57
57:   def sum(identity = 0, &block)
58:     return identity unless size > 0
59: 
60:     if block_given?
61:       map(&block).sum
62:     else
63:       inject { |sum, element| sum + element }
64:     end
65:   end

[Validate]