diff options
| -rw-r--r-- | activesupport/lib/active_support/core_ext/enumerable.rb | 22 | ||||
| -rw-r--r-- | activesupport/test/core_ext/enumerable_test.rb | 5 |
2 files changed, 26 insertions, 1 deletions
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb index e451e9933a..fd94bc051f 100644 --- a/activesupport/lib/active_support/core_ext/enumerable.rb +++ b/activesupport/lib/active_support/core_ext/enumerable.rb @@ -64,8 +64,28 @@ module Enumerable end end + # 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 + # + def each_with_object(memo, &block) + returning memo do |memo| + each do |element| + block.call(element, memo) + end + end + end unless [].respond_to?(:each_with_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}" } diff --git a/activesupport/test/core_ext/enumerable_test.rb b/activesupport/test/core_ext/enumerable_test.rb index 2315d8f3db..deb9b7544d 100644 --- a/activesupport/test/core_ext/enumerable_test.rb +++ b/activesupport/test/core_ext/enumerable_test.rb @@ -58,6 +58,11 @@ class EnumerableTests < Test::Unit::TestCase assert_equal Payment.new(0), [].sum(Payment.new(0)) end + def test_each_with_object + result = %w(foo bar).each_with_object({}) { |str, hsh| hsh[str] = str.upcase } + assert_equal({'foo' => 'FOO', 'bar' => 'BAR'}, result) + end + def test_index_by payments = [ Payment.new(5), Payment.new(15), Payment.new(10) ] assert_equal({ 5 => payments[0], 15 => payments[1], 10 => payments[2] }, |