121 lines
3.6 KiB
Ruby
121 lines
3.6 KiB
Ruby
require 'active_support/ordered_hash'
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module Enumerable
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# Ruby 1.8.7 introduces group_by, but the result isn't ordered. Override it.
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remove_method(:group_by) if [].respond_to?(:group_by) && RUBY_VERSION < '1.9'
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# Collect an enumerable into sets, grouped by the result of a block. Useful,
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# for example, for grouping records by date.
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#
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# Example:
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#
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# latest_transcripts.group_by(&:day).each do |day, transcripts|
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# p "#{day} -> #{transcripts.map(&:class).join(', ')}"
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# end
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# "2006-03-01 -> Transcript"
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# "2006-02-28 -> Transcript"
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# "2006-02-27 -> Transcript, Transcript"
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# "2006-02-26 -> Transcript, Transcript"
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# "2006-02-25 -> Transcript"
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# "2006-02-24 -> Transcript, Transcript"
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# "2006-02-23 -> Transcript"
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def group_by
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assoc = ActiveSupport::OrderedHash.new
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each do |element|
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key = yield(element)
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if assoc.has_key?(key)
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assoc[key] << element
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else
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assoc[key] = [element]
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end
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end
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assoc
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end unless [].respond_to?(:group_by)
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# Calculates a sum from the elements. Examples:
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#
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# payments.sum { |p| p.price * p.tax_rate }
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# payments.sum(&:price)
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#
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# The latter is a shortcut for:
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#
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# payments.inject { |sum, p| sum + p.price }
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#
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# It can also calculate the sum without the use of a block.
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#
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# [5, 15, 10].sum # => 30
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# ["foo", "bar"].sum # => "foobar"
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# [[1, 2], [3, 1, 5]].sum => [1, 2, 3, 1, 5]
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#
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# The default sum of an empty list is zero. You can override this default:
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#
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# [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
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#
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def sum(identity = 0, &block)
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if block_given?
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map(&block).sum(identity)
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else
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inject { |sum, element| sum + element } || identity
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end
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end
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# Iterates over a collection, passing the current element *and* the
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# +memo+ to the block. Handy for building up hashes or
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# reducing collections down to one object. Examples:
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#
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# %w(foo bar).each_with_object({}) { |str, hsh| hsh[str] = str.upcase } #=> {'foo' => 'FOO', 'bar' => 'BAR'}
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#
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# *Note* that you can't use immutable objects like numbers, true or false as
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# the memo. You would think the following returns 120, but since the memo is
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# never changed, it does not.
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#
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# (1..5).each_with_object(1) { |value, memo| memo *= value } # => 1
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#
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def each_with_object(memo, &block)
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memo.tap do |m|
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each do |element|
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block.call(element, m)
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end
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end
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end unless [].respond_to?(:each_with_object)
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# Convert an enumerable to a hash. Examples:
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#
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# people.index_by(&:login)
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# => { "nextangle" => <Person ...>, "chade-" => <Person ...>, ...}
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# people.index_by { |person| "#{person.first_name} #{person.last_name}" }
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# => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
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#
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def index_by
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inject({}) do |accum, elem|
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accum[yield(elem)] = elem
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accum
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end
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end
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# Returns true if the collection has more than 1 element. Functionally equivalent to collection.size > 1.
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# 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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def many?(&block)
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size = block_given? ? select(&block).size : self.size
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size > 1
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end
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# Returns true if none of the elements match the given block.
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#
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# success = responses.none? {|r| r.status / 100 == 5 }
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#
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# This is a builtin method in Ruby 1.8.7 and later.
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def none?(&block)
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!any?(&block)
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end unless [].respond_to?(:none?)
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# The negative of the Enumerable#include?. Returns true if the collection does not include the object.
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def exclude?(object)
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!include?(object)
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end
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end
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