category.rb

class Category < ActiveRecord::Base
  configure do
    option :sort do
      default  'alphabetical'
      restrict 'alphabetical', 'manual'
    end

    option :limit do
      format 'fixnum'
    end

    option :price_filter do
      format    'float'
      modifiers 'eq', 'lt', 'gt', 'lte', 'gte'
      multiple  true
    end
  end
end

example.rb

>> category = Category.create(:name => 'Vinyl Records')
=> #<Category id: 1, name: "Vinyl Records", created_at: "2011-08-03 15:46:11", updated_at: "2011-08-03 15:46:11">

?> category.settings
=> #<ActiveConfiguration::SettingManager:0x10e7d1950 @configurable=#<Category id: 1, name: "Vinyl Records", created_at: "2011-08-03 15:46:11", updated_at: "2011-08-03 15:46:11">>

?> category.settings[:sort]
=> {:value=>"alphabetical", :modifier=>nil}

?> category.settings[:sort][:value]
=> "alphabetical"

?> category.settings[:sort][:value] = 'manual'
=> "manual"

?> category.settings[:price_filter]
=> []

?> category.settings[:price_filter] = [{:modifier => 'gt', :value => 10.00}, {:modifier => 'lte', :value => 25.00}]
=> [{:value=>10.0, :modifier=>"gt"}, {:value=>25.0, :modifier=>"lte"}]

?> category.save
=> true

?> category.settings[:sort][:value]
=> "manual"

?> category.settings[:price_filter]
=> [{:value=>10.0, :modifier=>"gt"}, {:value=>25.0, :modifier=>"lte"}]

generate.rb

rails g active_configuration:install

install-gem.rb

gem 'active_configuration'

migrate.rb

rake db:migrate