loggable.rb

loggable.rb

require "logger"

module Loggable
  attr_accessor :logger

  def initialize(*args, logger: nil, **options, &block)
    @logger = logger || default_logger
    super(*args, **options, &block)
  end

  protected

  def default_logger
    Logger.new(default_logger_io).tap do |log|
      log.progname = default_logger_progname
      log.formatter = default_logger_formatter
    end
  end

  def default_logger_io
    $stdout
  end

  def default_logger_progname
    self.class.name
  end

  def default_logger_formatter
    proc do |severity, datetime, progname, msg|
      tid = Thread.current.name || Thread.current.native_thread_id
      thread_info = Thread.list.size > 1 ? "[T:#{tid}]" : ""
      "[#{datetime}] #{severity} #{progname}#{thread_info} -- #{msg}\n"
    end
  end
end

loggable_demo.rb

require_relative "loggable"

# Now you can do:

class OrderProcessor
  prepend Loggable

  def initialize(order_id)
    @order_id = order_id
    logger.info { "Processing order ##{@order_id}" }
  end
end

# Default logger
OrderProcessor.new(42)

# Custom loggers
OrderProcessor.new(42, logger: Rails.logger)
OrderProcessor.new(42, logger: Logger.new("orders.log"))