Command Pattern - null listener

r_j-utils-nill_listener.rb

module RJ
  module Utils
    module NullListener
      # allows for injection of a different class for null_listeners
      #
      attr_writer :null_listener_class

      private

      # make available a null_listener that uses the null object pattern
      #
      def null_listener
        _null_listener_source.call
      end

      # creates an anonymous class based on Naught library for null listener
      # - allows for dependency injection to enable swap out of class
      #
      def _null_listener_class
        @null_listener_class ||= Naught.build
      end

      # proc which when called instantiates an instance of null listener class
      #
      def _null_listener_source
        _null_listener_class.public_method(:new)
      end
    end
  end
end