Module: Enumerable
- Defined in:
- lib/active_support/core_ext/enumerable.rb,
lib/active_support/json/encoders/enumerable.rb
Instance Method Summary collapse
-
#group_by ⇒ Object
Collect an enumerable into sets, grouped by the result of a block.
-
#index_by ⇒ Object
Convert an enumerable to a hash.
-
#sum(identity = 0, &block) ⇒ Object
Calculates a sum from the elements.
-
#to_json(options = {}) ⇒ Object
Returns a JSON string representing the enumerable.
Instance Method Details
#group_by ⇒ Object
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"
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# File 'lib/active_support/core_ext/enumerable.rb', line 20 def group_by inject ActiveSupport::OrderedHash.new do |grouped, element| (grouped[yield(element)] ||= []) << element grouped end end |
#index_by ⇒ Object
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 ...>, ...}
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# File 'lib/active_support/core_ext/enumerable.rb', line 63 def index_by inject({}) do |accum, elem| accum[yield(elem)] = elem accum end end |
#sum(identity = 0, &block) ⇒ Object
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)
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# File 'lib/active_support/core_ext/enumerable.rb', line 46 def sum(identity = 0, &block) return identity unless size > 0 if block_given? map(&block).sum else inject { |sum, element| sum + element } end end |
#to_json(options = {}) ⇒ Object
Returns a JSON string representing the enumerable. Any options
given will be passed on to its elements. For example:
users = User.find(:all)
# => users.to_json(:only => :name)
will pass the :only => :name
option to each user.
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# File 'lib/active_support/json/encoders/enumerable.rb', line 9 def to_json( = {}) #:nodoc: "[#{map { |value| ActiveSupport::JSON.encode(value, ) } * ', '}]" end |