Ruby: Logging module with class names, output to both STDOUT and file

logger.rb

require 'logger'

module Logging
  class MultiDelegator
    def initialize(*targets)
      @targets = targets
    end

    def self.delegate(*methods)
      methods.each do |m|
        define_method(m) do |*args|
          @targets.map { |t| t.send(m, *args) }
        end
      end
      self
    end

    class << self
      alias to new
    end
  end

  def logger
    @logger ||= Logging.logger_for(self.class.name)
  end

  # Use a hash class-ivar to cache a unique Logger per class:
  @loggers = {}

  class << self
    def logger_for(classname)
      @loggers[classname] ||= configure_logger_for(classname)
    end

    def configure_logger_for(classname)
      # Set up your log file
      file = File.open(
        'log/log_file.log',
        File::WRONLY | File::APPEND | File::CREAT
      )
      # Force the buffer to flush on each write
      file.sync = true
      logger = Logger.new MultiDelegator.delegate(:write, :close).to(STDOUT, file)
      logger.progname = classname
      logger
    end
  end
end

# Then, in class files

class Thing
  # Mix in the ability to log stuff ...
  include Logging

  # Much logging and output. Wow
  def foo(bar)
    logger.warn "About to foo the bar"
    # commence foo-ing
  end
end