# File lib/mongoid/persistence/atomic/bit.rb, line 19
        def persist
          prepare do
            current = document[field]
            return nil unless current
            document[field] = value.inject(current) do |result, (bit, val)|
              result = result & val if bit.to_s == "and"
              result = result | val if bit.to_s == "or"
              result
            end
            document[field].tap do
              collection.update(document.atomic_selector, operation("$bit"), options)
              document.remove_change(field)
            end
          end
        end