順序付きのHash OrderedHash
$ script/console Loading development environment (Rails 2.3.2) >> RUBY_VERSION => "1.8.7" >> ActiveSupport::OrderedHash.new(:a => 1, :b => 2) => #<OrderedHash {}> >> ActiveSupport::OrderedHash.new([[:a, 1], [:b, 2]]) => #<OrderedHash {}> >> hash = ActiveSupport::OrderedHash.new => #<OrderedHash {}> >> hash[:a] = 1 => 1 >> hash[:b] = 2 => 2 >> hash => #<OrderedHash {:a=>1, :b=>2}>
Rails と Ruby の Ordered Hash について
HashとActiveSupport::OrderedHashのmergeの挙動が異なる
Rails 2.3 の ActiveSupport::OrderedHash がなんか変