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
[ show source ]
# File activesupport/lib/active_support/core_ext/enumerable.rb, line 77
77: def each_with_object(memo, &block)
78: memo.tap do |m|
79: each do |element|
80: block.call(element, m)
81: end
82: end
83: end
The negative of the Enumerable#include?. Returns true if the collection does not include the object.
[ show source ]
# File activesupport/lib/active_support/core_ext/enumerable.rb, line 117
117: def exclude?(object)
118: !include?(object)
119: 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"
[ show source ]
# File 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 ...>, ...}
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# File activesupport/lib/active_support/core_ext/enumerable.rb, line 92
92: def index_by
93: inject({}) do |accum, elem|
94: accum[yield(elem)] = elem
95: accum
96: end
97: 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.
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# File activesupport/lib/active_support/core_ext/enumerable.rb, line 101
101: def many?(&block)
102: size = block_given? ? select(&block).size : self.size
103: size > 1
104: end
Returns true if none of the elements match the given block.
success = responses.none? {|r| r.status / 100 == 5 }
This is a builtin method in Ruby 1.8.7 and later.
[ show source ]
# File activesupport/lib/active_support/core_ext/enumerable.rb, line 111
111: def none?(&block)
112: !any?(&block)
113: 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)
[ show source ]
# File activesupport/lib/active_support/core_ext/enumerable.rb, line 57
57: def sum(identity = 0, &block)
58: if block_given?
59: map(&block).sum(identity)
60: else
61: inject { |sum, element| sum + element } || identity
62: end
63: end