Module: Enumerable
- Included in:
- ActiveSupport::Dependencies::WatchStack
- Defined in:
- lib/active_support/json/encoding.rb,
lib/active_support/core_ext/enumerable.rb
Instance Method Summary collapse
-
#as_json(options = nil) ⇒ Object
:nodoc:.
-
#each_with_object(memo) ⇒ Object
Iterates over a collection, passing the current element and the
memo
to the block. -
#exclude?(object) ⇒ Boolean
The negative of the
Enumerable#include?
. -
#group_by ⇒ Object
Collect an enumerable into sets, grouped by the result of a block.
-
#index_by ⇒ Object
Convert an enumerable to a hash.
-
#many? ⇒ Boolean
Returns true if the enumerable has more than 1 element.
-
#sum(identity = 0, &block) ⇒ Object
Calculates a sum from the elements.
Instance Method Details
#as_json(options = nil) ⇒ Object
:nodoc:
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# File 'lib/active_support/json/encoding.rb', line 206 def as_json( = nil) #:nodoc: to_a.as_json() end |
#each_with_object(memo) ⇒ Object
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
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# File 'lib/active_support/core_ext/enumerable.rb', line 79 def each_with_object(memo) return to_enum :each_with_object, memo unless block_given? each do |element| yield element, memo end memo end |
#exclude?(object) ⇒ Boolean
The negative of the Enumerable#include?
. Returns true if the collection does not include the object.
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# File 'lib/active_support/core_ext/enumerable.rb', line 114 def exclude?(object) !include?(object) end |
#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 22 def group_by return to_enum :group_by unless block_given? assoc = ActiveSupport::OrderedHash.new each do |element| key = yield(element) if assoc.has_key?(key) assoc[key] << element else assoc[key] = [element] end end assoc 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 94 def index_by return to_enum :index_by unless block_given? Hash[map { |elem| [yield(elem), elem] }] end |
#many? ⇒ Boolean
Returns true if the enumerable has more than 1 element. Functionally equivalent to enum.to_a.size > 1. Can be called with a block too, much like any?, so people.many? { |p| p.age > 26 }
returns true if more than one person is over 26.
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# File 'lib/active_support/core_ext/enumerable.rb', line 101 def many? cnt = 0 if block_given? any? do |element| cnt += 1 if yield element cnt > 1 end else any?{ (cnt += 1) > 1 } 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(0) { |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 58 def sum(identity = 0, &block) if block_given? map(&block).sum(identity) else inject(:+) || identity end end |