method_profiling.rb

require 'active_support/core_ext/module'
require 'active_support/core_ext/benchmark'

Object.singleton_class.class_eval do
  def profile_methods(*names)
    names.each do |name|
      case name
        when Regexp
          profiling_methods.grep(name).each { |match| profile_method(match) }
        else
          _profile_method(name)
      end
    end
  end

  def profile_methods!
    profiling_methods.each { |method| profile_method(method) }
  end

  def profiling_methods
    methods = self.instance_methods(false)
    methods.delete(:initialize)
    methods
  end

  alias_method :profile_method, :profile_methods

  private

  def _profile_method(method_name)
    method_name_with_profiling, method_name_without_profiling = build_profiling_method_names(method_name)
    unless method_defined?(method_name_with_profiling)
      define_method method_name_with_profiling do |*args, &block|
        value = nil
        time = Benchmark.ms { value = send(method_name_without_profiling, *args, &block) }
        arg_values = args.inspect
        arg_values = arg_values[/^\[(.+)\]$/, 1] || ""
        arg_values = arg_values.size > 180 ? [arg_values[0..180], "..."].join : arg_values
        !arg_values == "" && arg_values = ["(", arg_values, ")"].join
        puts "(%010.2fms) #{self.class}##{method_name}#{arg_values}" % [time]
        value
      end

      alias_method_chain method_name, :profiling
    end
  end

  def build_profiling_method_names(target)
    aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1
    [:"#{aliased_target}_with_profiling#{punctuation}", :"#{aliased_target}_without_profiling#{punctuation}"]
  end
end

Module.class_eval do
  def profile_methods!
    local_constants.each do |constant|
      klass = const_get(constant)
      if klass.respond_to?(:profiling_methods)
        klass.profiling_methods.each { |method| klass.profile_method(method) }
      end
    end
  end
end

output.txt

(0000000.00ms) Namespace::Awesome#i_am
(0000000.01ms) Greeter#say_hello
Hello!

usage.rb

require_relative 'method_profiling'

class Greeter
  def say_hello
    puts "Hello!"
  end

  def say_yeah
    puts "Yeah!"
  end
end

module Namespace
  class Awesome
    def i_am
    end
  end
end

Greeter.profile_methods /^say_/
Namespace.profile_methods!

Greeter.new.say_hello
Namespace::Awesome.new.i_am