flagable.rb

module ActiveRecord
  module Acts
    module AsFlagable
      def self.included(base)
        base.extend ClassMethods
      end
  
      module ClassMethods
        def acts_as_flagable(options)
          unless flagable?
            cattr_accessor :flag_values
            self.flag_values = options
        
            after_initialize :set_flag_attributes
            before_save :set_flag_mask
        
            attr_accessor *options.keys
        
            options.each_key do |flag|
              define_method "#{flag}?" do
                (flags & flag_values[flag]) == flag_values[flag]
              end
            end
        
            include InstanceMethods
          end
        end
    
        def flagable?
          self.included_modules.include?(InstanceMethods)
        end
      end
  
      module InstanceMethods
        private
        def set_flag_attributes
          flag_values.each_key do |flag|
            if self.send("#{flag}?".to_sym)
              self.send("#{flag}=".to_sym, true)
            else
              self.send("#{flag}=".to_sym, false)
            end
          end
        end

        def set_flag_mask
          self.flags = 0
          flag_values.each do |flag, value|
            if self.send(flag)
              self.flags = self.flags | value
            end
          end
        end
      end
    end
  end
end

ActiveRecord::Base.send(:include, ActiveRecord::Acts::AsFlagable)

should_be_flagable.rb

class ActiveSupport::TestCase
  
  def self.should_be_flagable(flags)
    should 'have a flag_values class method' do
      assert_equal flags, self.class.described_type.flag_values
    end
    
    should 'be flagable?' do
      assert self.class.described_type.flagable?
    end
    
    flags.each do|flag, value|
      should_have_instance_methods "#{flag}", "#{flag}=", "#{flag}?"
      
      should "correctly set the #{flag} instance variable to true on initiation" do
        subject.send("#{flag}=", true)
        subject.save!
        
        found_record = self.class.described_type.find(subject.id)
        assert found_record.send("#{flag}?")
      end
      
      should "correctly set the #{flag} instance variable to false on initiation" do
        subject.send("#{flag}=", false)
        subject.save!
        
        found_record = self.class.described_type.find(subject.id)
        assert !found_record.send("#{flag}?")
      end
    end
  end

end