virtual formatted date attribute

formatted_date_attribute.rb

module FormattedDateAttributes
  # Define virtual formatted date attribute
  #
  # formatted_date_attribute(:start_at, :end_at, :format => :default)
  # formatted_date_attribute(:start_at, :end_at, :format => '%d/%m/%y')
  #
  # format parameter can be a symbol from config/initializers/date_time_formats.rb or any
  # string format that will work with Date#strftime and DateTime.strptime methods
  def formatted_date_attributes(*args)
    options = { :format => :default }.merge(args.extract_options!)

    args.each do |attr_name|
      formatted_name = "formatted_#{attr_name}"

      define_method(formatted_name) do
        return self[attr_name] unless self[attr_name]

        options[:format].is_a?(Symbol) ? self[attr_name].to_s(options[:format]) : self[attr_name].strftime(options[:format])
      end

      define_method("#{formatted_name}=") do |value|
        return if value.blank?

        format = if options[:format].is_a?(Symbol)
          column_for_attribute(attr_name).type == :date ? Date::DATE_FORMATS[options[:format]] : Time::DATE_FORMATS[options[:format]]
        else
          options[:format]
        end

        self[attr_name] = DateTime.strptime(value, format)
      end
    end
  end
end