signed_ids.rb

class Order < ActiveRecord::Base
  
  SECRET = '3a9392e86049546fcff5e21e3c89564deb8bd9d4'
  
  def self.find_by_token(token)
    id, sig = token.split('-')
    record = find(id)
    if record.nil? || token != record.token
      raise ActiveRecord::RecordNotFound, "invalid sig"
    end
    record
  end
  
  def token
    sig = Digest::SHA1.hexdigest(id.to_s + SECRET)[0, 9]
    [id, sig].join('-')
  end

end