Bitmask Example

bitmask.rb

# model code 
property :paths_mask, Integer

NODE_PATH = %w(path_1 path_2 path_3 path_4)

def paths=(paths)
  self.paths_mask = (paths & NODE_PATH).map { |r| 2**NODE_PATH.index(r) }.sum
end

def paths
  NODE_PATH.reject do |r|
    ((paths_mask || 0) & 2**NODE_PATH.index(r)).zero?
  end
end

# not using is_a? here because Devise doesn't like that
def is_an?(path)
  paths.include?(path.to_s)
end

# view code in haml
%h2 Paths this Question Applies to
- for path in Question::NODE_PATH
  %p
    = check_box_tag "question[paths][]", path, @question.paths.include?(path)
    = path.humanize.titleize
  = hidden_field_tag "question[paths][]", ""