From: Reginald Tan <redge.tan@...>
Date: 2011-09-30T13:30:52+09:00
Subject: using alias_method before function definition

Hi guys, I'm having problems with using alias_method. When i run this
code, I'm getting  undefined method `shout' for class `Person'
(NameError) since I'm using alias_method on a function that is probably
not defined yet. The example would work if I put the profile method
after the method name, but is there a cleaner solution to make this
work? This post (http://www.ruby-forum.com/topic/100587) seem to solve
this problem using "method_added" callback but i hope i could use a
different approach

module SimpleProfiler
  def profile(*methods)
    methods.each do |method|
      send :alias_method, "orig_#{method}", method

      define_method method do |name|
        before = Time.now
        send "orig_#{method}", name
        after = Time.now
        puts sprintf("%s: %.4fs", method, after - before)
      end
    end
  end
end

class Person
  extend SimpleProfiler
  profile :shout

  def shout(name)
    sleep(1)
    puts name
  end
end

p = Person.new
p.shout("reg")

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