logging when methods begin and when methods end by prepending

before-after-method-logging.rb

require 'logger'

module Logging
  def self.prepended(base)
    target_methods = base.instance_methods - Object.methods
    target_methods.each do |method|
      define_method(method) do |*args|
        log.debug "[Start] #{base}##{method}"
        ret = super(*args)
        log.debug "[End] #{base}##{method}"
        return ret
      end
    end
  end

  private

  def log
    @log ||= Logger.new $stdout
  end
end

class A
  def hoge
    puts 'HOGE'
  end

  def fuga
    puts "FUGA"
  end

  # this line has to be after all method definitions
  prepend Logging

end

A.new.hoge
A.new.fuga