def format_null(params = {}, &block)
      component[:null_formatter] = (params[:using] or block)
      component[:null_formatter] ||= proc do |value|
        params[:with] % value
      end
    end
def format_null(params = {}, &block)
      component[:null_formatter] = (params[:using] or block)
      component[:null_formatter] ||= proc do |value|
        params[:with] % value
      end
    end
Defines a formatter to null values.

 === Args

 +params+::
   A hash with params in case a block is not given:
     - :using defines the component to use
     - :with defines the format to use