Example to show how to define a hook before a method called

method_hook.rb

class Base
  def self.method_added(name)
    if /hook/.match(name.to_s) or method_defined?("#{name}_without_hook")
      return
    end
    hook = "def #{name}_hook\n p 'Method #{name} has been called'\n #{name}_without_hook\nend"
    self.class_eval(hook)

    a1 = "alias #{name}_without_hook #{name}"
    self.class_eval(a1)

    a2 = "alias #{name} #{name}_hook"
    self.class_eval(a2)
  end
  def a
    p "a called."
  end
  def b
    p "b called."
  end
end
t1 = Base.new
t1.a
t1.b
t1.a
t1.b