Shared logger setup

shared_logger.rb

require 'logger'
require 'singleton'

module Logging
  def logger
    Logger.instance
  end

  class Logger < ::Logger
    include Singleton

    def initialize
      puts 'Initializing logger...'
      super(STDOUT)
      self.level = Logger::INFO
      self
    end
  end
end


class Animal
  include Logging

  def talk(sound)
    puts "#{sound}!!"
    logger.info(self.class) do
      "Said #{sound}, object_id = #{object_id}, logger_object_id = #{logger.object_id}"
    end
  end
end

class Dog < Animal
  def bark
    talk 'Woof'
  end
end

class Cat < Animal
  def meow
    talk 'Meow'
  end
end

dog1, dog2 = 2.times.map { Dog.new }
cat1, cat2 = 2.times.map { Cat.new }

dog1.bark # Initializes the logger, once
dog2.bark # Uses the same logger instance
cat1.meow # Same
cat2.meow # Etc.