Enumeration Support

# based on an idea by Gavin Mulligan
# http://gavin-mulligan.tumblr.com/post/3825225016/simple-rails-3-enumerations

# this version differs because
# * it returns StringInquirers rather than symbols, 
#   because I'll take any excuse to use StringInquirers
# * It uses meta program methods directly rather than class_eval
# * It auto-loads itself into ActiveRecord::Base
# * It supports a default option that uses default_value_for to set a default
#

# Usage:
# class Content < ActiveRecord::Base
#   enumeration :state %w(draft for_approval approved published), :default => "draft"
# end 

# c = Content.new
# c.state.draft?
# c.state.approved?

module EnumerationSupport
  def enumeration(name, values, options = {})
    const_name = name.to_s.pluralize.upcase
    const_set(const_name, values.map{ |val| val.to_s })
    validates name.to_sym, :presence => true,
        :inclusion => {:in => const_get(const_name.to_sym),
            :message => self.bad_enum_message(const_get(const_name.to_s))}

    define_method name.to_sym do
      ::ActiveSupport::StringInquirer.new("#{read_attribute(name)}")
    end

    define_method :"#{name}=" do |value|
      write_attribute name.to_sym, value.to_s
    end

    if options[:default].present?
      default_value_for name.to_sym, options[:default].to_s
    end
  end

  protected

  def bad_enum_message(enum)
    "is not in the set (#{enum.join(', ')})"
  end
end

ActiveRecord::Base.send(:extend, EnumerationSupport)