Method tracking. Could be used to unobtrusively track method calls

object_tracker.rb

module ObjectTracker
  def track(*args)
    @__tracking ||= []
    args.each { |arg| @__tracking << arg unless tracking?(arg) }
  end

  def track!(*args)
    track(*args)
    start_tracking!
  end

  def track_all!
    track!(*(methods + instance_methods))
  end

  def tracking?(method_name)
    @__tracking.include?(method_name)
  end

  def start_tracking!
    mod = Module.new
    @__tracking.each do |method_name|
      mod.module_eval <<-RUBY, __FILE__, __LINE__
        def #{method_name}(*args, &block)
          msg = "called #{method_name} "
          msg << "with " << args.join(', ') << " " if args.any?
          msg << "from #{__FILE__}:#{__LINE__}"
          puts msg
          super
        end
      RUBY
    end

    mod.module_eval <<-RUBY, __FILE__, __LINE__
      def self.prepended(base)
        base.extend(self)
      end
    RUBY

    prepend(mod)
  end
end

class Dog
  extend ObjectTracker

  def woof!
    'woofing so hard right now'
  end

  def go(name)
    "Going to #{name}'s house"
  end
end

Dog.track_all!
Dog
#=> inspect called from (irb):27
Dog.new.go('Ryan')
#=> called new from (irb):27
#=> called go with Ryan from (irb):27
#=> Going to Ryan's house