trace_module.rb

trace.rb

module Foobar
  # the extend class macro takes all instance methods and makes them
  # into class methods
  extend Foobar
  # instead of doing self.say_foobar
  # remove the self, but then "extend"
  def say_foobar
    puts "foobar"
  end
end

def tick args
  Tracing.trace_method_for_module! Foobar, :say_foobar
  Foobar.say_foobar
end

module Tracing
  def self.trace_method_for_module! klass, m
    $already_tracing ||= {}
    $already_tracing[klass] ||= {}
    return if $already_tracing[klass][m]

    klass.module_eval do
      original_method_name = m
      trace_method_name = "trace_method_#{Time.now.to_i}"
      alias_method trace_method_name, m
      puts "#{m} has been aliased"
      puts "Tracing #{m} on #{klass}."
      $already_tracing[klass][m] = true

      define_method(m) do |*args|
        parameters = "#{args}"[1..-2]
        puts "method: #{m}"
        puts "params: #{parameters}"
        result = send(trace_method_name, *args)
        puts "success: #{m}"
        puts "result: #{result}"
        puts "nil? #{result.nil?}"
        result
      rescue Exception => e
        puts "failed: #{m}"
        raise e
      end
    end
  end
end