1 require 'active_support/ordered_hash'
4 # Ruby 1.8.7 introduces group_by, but the result isn't ordered. Override it.
5 remove_method(:group_by) if [].respond_to
?(:group_by) && RUBY_VERSION < '1.9'
7 # Collect an enumerable into sets, grouped by the result of a block. Useful,
8 # for example, for grouping records by date.
12 # latest_transcripts.group_by(&:day).each do |day, transcripts|
13 # p "#{day} -> #{transcripts.map(&:class).join(', ')}"
15 # "2006-03-01 -> Transcript"
16 # "2006-02-28 -> Transcript"
17 # "2006-02-27 -> Transcript, Transcript"
18 # "2006-02-26 -> Transcript, Transcript"
19 # "2006-02-25 -> Transcript"
20 # "2006-02-24 -> Transcript, Transcript"
21 # "2006-02-23 -> Transcript"
23 assoc
= ActiveSupport
::OrderedHash.new
28 if assoc
.has_key
?(key
)
31 assoc
[key
] = [element
]
36 end unless [].respond_to
?(:group_by)
38 # Calculates a sum from the elements. Examples:
40 # payments.sum { |p| p.price * p.tax_rate }
41 # payments.sum(&:price)
43 # The latter is a shortcut for:
45 # payments.inject { |sum, p| sum + p.price }
47 # It can also calculate the sum without the use of a block.
49 # [5, 15, 10].sum # => 30
50 # ["foo", "bar"].sum # => "foobar"
51 # [[1, 2], [3, 1, 5]].sum => [1, 2, 3, 1, 5]
53 # The default sum of an empty list is zero. You can override this default:
55 # [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
57 def sum(identity
= 0, &block
)
58 return identity
unless size
> 0
63 inject
{ |sum
, element
| sum
+ element
}
67 # Iterates over a collection, passing the current element *and* the
68 # +memo+ to the block. Handy for building up hashes or
69 # reducing collections down to one object. Examples:
71 # %w(foo bar).each_with_object({}) { |str, hsh| hsh[str] = str.upcase } #=> {'foo' => 'FOO', 'bar' => 'BAR'}
73 # *Note* that you can't use immutable objects like numbers, true or false as
74 # the memo. You would think the following returns 120, but since the memo is
75 # never changed, it does not.
77 # (1..5).each_with_object(1) { |value, memo| memo *= value } # => 1
79 def each_with_object(memo
, &block
)
82 block
.call(element
, m
)
85 end unless [].respond_to
?(:each_with_object)
87 # Convert an enumerable to a hash. Examples:
89 # people.index_by(&:login)
90 # => { "nextangle" => <Person ...>, "chade-" => <Person ...>, ...}
91 # people.index_by { |person| "#{person.first_name} #{person.last_name}" }
92 # => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
95 inject({}) do |accum
, elem
|
96 accum
[yield(elem
)] = elem
101 # Returns true if the collection has more than 1 element. Functionally equivalent to collection.size > 1.
102 # Works with a block too ala any?, so people.many? { |p| p.age > 26 } # => returns true if more than 1 person is over 26.
104 size
= block_given
? ? select(&block
).size
: self.size