mongo-ruby-driver/lib/mongo/util/ordered_hash.rb

# --
# Copyright (C) 2008 10gen Inc.
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License, version 3, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License
# for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# ++

# A hash in which the order of keys are preserved.
class OrderedHash < Hash

  attr_accessor :ordered_keys

  def keys
    @ordered_keys || []
  end

  def []=(key, value)
    @ordered_keys ||= []
    @ordered_keys << key unless @ordered_keys.include?(key)
    super(key, value)
  end

  def each
    @ordered_keys ||= []
    @ordered_keys.each { |k| yield k, self[k] }
  end

  def merge(other)
    @ordered_keys ||= []
    @ordered_keys += other.keys # unordered if not an OrderedHash
    super(other)
  end

end