Ruby - share logger instance among module/classes

Question

Working on a little Ruby script that goes out to the web and crawls various services. I\'ve got a module with several classes inside:

module Crawler
  class          


        

Answer 1

As Zenagray points out, logging from class methods was left out of Jacob's answer. A small addition solves that:

require 'logger'

module Logging
  class << self
    def logger
      @logger ||= Logger.new($stdout)
    end

    def logger=(logger)
      @logger = logger
    end
  end

  # Addition
  def self.included(base)
    class << base
      def logger
        Logging.logger
      end
    end
  end

  def logger
    Logging.logger
  end
end

The intended use is via "include":

class Dog
  include Logging

  def self.bark
    logger.debug "chirp"
    puts "#{logger.__id__}"
  end

  def bark
    logger.debug "grrr"
    puts "#{logger.__id__}"
  end
end

class Cat
  include Logging

  def self.bark
    logger.debug "chirp"
    puts "#{logger.__id__}"
  end

  def bark
    logger.debug "grrr"
    puts "#{logger.__id__}"
  end
end

Dog.new.bark
Dog.bark
Cat.new.bark
Cat.bark

Produces:

D, [2014-05-06T22:27:33.991454 #2735] DEBUG -- : grrr
70319381806200
D, [2014-05-06T22:27:33.991531 #2735] DEBUG -- : chirp
70319381806200
D, [2014-05-06T22:27:33.991562 #2735] DEBUG -- : grrr
70319381806200
D, [2014-05-06T22:27:33.991588 #2735] DEBUG -- : chirp
70319381806200

Note the id of the logger is the same in all four cases. If you want a different instance for each class, then don't use Logging.logger, rather use self.class.logger:

require 'logger'

module Logging
  def self.included(base)
    class << base
      def logger
        @logger ||= Logger.new($stdout)
      end

      def logger=(logger)
        @logger = logger
      end
    end
  end

  def logger
    self.class.logger
  end
end

The same program now produces:

D, [2014-05-06T22:36:07.709645 #2822] DEBUG -- : grrr
70350390296120
D, [2014-05-06T22:36:07.709723 #2822] DEBUG -- : chirp
70350390296120
D, [2014-05-06T22:36:07.709763 #2822] DEBUG -- : grrr
70350390295100
D, [2014-05-06T22:36:07.709791 #2822] DEBUG -- : chirp
70350390295100

Note that the first two id's are the same but are different from the 2nd two ids showing that we have two instances -- one for each class.