How to implement a singleton model

Question

I have a site in rails and want to have site-wide settings. One part of my app can notify the admin by SMS if a specific event happens. This is an example of a feature that

Answer 1

class Constant < ActiveRecord::Base
  after_initialize :readonly!

  def self.const_missing(name)
    first[name.to_s.downcase]
  end
end

Constant::FIELD_NAME