A simple lib to make an active record class work with a single row. Not sure how I feel about it yet, but it really came in handy in a current app.

active_record_singleton.rb

module ActiveRecordSingleton
  def self.included(base)
    base.class_eval do
      class << self
        delegate :attributes, :save, :save!, :update_attribute, :update_attributes, :update_attributes!, :update_column, to: 'instance'

        [:new, :create, :create!, :destroy, :destroy_all, :delete, :delete_all].each do |method_name|
          undef_method method_name
        end

        def instance
          @@singleton ||= self.first_or_create!
        end
      end

      [:destroy, :delete, :clone, :dup].each do |method_name|
        undef_method method_name
      end

      column_names.each do |column_name|
        define_singleton_method column_name.to_sym do
          instance.send(column_name.to_sym)
        end

        define_singleton_method :"#{column_name}=" do |value|
          instance.send(:"#{column_name}=", value)
        end
      end
    end
  end
end

settings.rb

class Settings < ActiveRecord::Base
  include ActiveRecordSingleton
end

Usage:

Settings.some_setting
Settings.some_setting = 'new_value'
Settings.save!
Settings.update_attributes(params[:settings])
Settings.new #=> Raises error

Could assign the instance to a constant:

class SettingsSingleton < ActiveRecord::Base
  self.table_name = 'settings'
end

Settings = SettingsSingleton.first_or_create!

@jeremy:

Thanks for that nugget!

Final code:

class SettingsSingleton < ActiveRecord::Base
  self.table_name = 'settings'
end

Settings = SettingsSingleton.first_or_create!

Settings.class_eval do
  [:destroy, :delete, :clone, :dup].each do |method_name|
    undef_method method_name
  end
end