In this gist we will try to add the logging functionality to the pre-existing Fixnum '/' method and learn how to do so in the process thro alias_method technique.

ruby logger.rb

require 'logger'
# Generally its a good practice to avoid global variables, but a good use of them would be in a logger constant
# you can try other Logger creation options such as
# Keep data for the current month only
# Logger.new('this_month.log', 'monthly')
# Keep data for today and the past 20 days.
# Logger.new('application.log', 20, 'daily')
# Start the log over whenever the log exceeds 100 megabytes in size.
# Logger.new('application.log', 0, 100 * 1024 * 1024)
$LOG = Logger.new('app.log', 'monthly')

class Fixnum
  # alias the original Fixnum division method
  alias_method :divide, :/
  # overriding division method to add logger functionality
  def /(denominator)
    $LOG.debug("Trying to divide #{self} By #{denominator}")
    begin
      return self.divide denominator
    rescue Exception => ex
      $LOG.error("Error occured (#{ex})")
      return nil
    end
  end
end

# trying it out...
(0..10).to_a.each { |i| puts 1 / i }